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First test if the fat channel display behaves for other functions like input and output metering and FX and auxiliary mixing. If the channel input meters work properly and the AUX and FX channel mixes are flakey, then suspect the 5 volt reference supplied to the pots might be unstable. This would require an oscilloscope to monitor. Almost all the pots and sliders except the input trim and a few at the output are actually .sampled by an A-D and the function is all done mathematically, digitally.

You may be able to isolate this behavior with the "locate" function by saving a scene of fader positions and then bring up locate and move a few sliders and see if the error position due too your change when locate is on is stable... if it is flakey, then likely the reference for the pots (also in common with the faders) is unstable.. This boils down to a flakey power supply if the symptoms match.

Hey Fredy thanks for your reply. Appreciated.

Well m not sure if its the power supply. As i still can record with or without phantom. Playback is fine, using the SL as my interface for nuendo and other daws, working nice.

So I tried what you've mentioned above.

1) I selected the INPUT button to monitor my input metering, it stayed there for like 2sec and then threw me back into the fat channel, i repeat the process and it did the same, takes me back to the channels fat-c
(same happens for the output, takes me back to the ground zero or the previous channel location i was)

2) I worked on your 2nd advice as well. I tried locating faders and saving the channel presets. Moving a fader slightly is like skipping led lights randomly, like if I move a db up it might go down 5-6 lights , or sometimes 3-4 lights up.

I'm totally confused now. So what if its the power supply. What should I be doing? I dont have presonus support/tech in my country. So all m left with are freelance techs and engineers.

Will appreciate your input

P.S Overhauling would make any difference? Like removing the cover and taking care of dust and all?

Looking forward to hear from you.

Check the inrush limiter RT1 on the PSU board... if it shows signs of cracking, replace it. Part is readily available from several sources.
I also had this behavior on a unit that got wet and the encoders for the fat channel were randomly sending in garbage causing FAT changes. Fixed that by driving into the encoders some CRC226. Using a piece of shrink fit pressed down over the shaft, put some of the 226 into the tubing and use an air compressor to drive the fluid into the encoders via the shaft to bearing gap.

I have the same problem. I can't get thru to Presonus tech support. Its happening to all knobs . I run live music weekly . I have adapted to a survival technique. Channel 1 is not used . Any changes to the fat channel ,fx, aux ect I select my channel make my changes and select channel 1 and hide there till I need to go out again .The wandering knobs only effect the channel selected so I keep it on channel one . Love the board Just want it fixed

I don't think I am having quite the same problem, but Something similar. At a recent show, running the classic 24.4.2 with VSL on OSX Yosemite and remote control on iOS 8.3, I shut off the fat channel EQ on the mainout and submit channels via the physical 24.4.2 but it would periodically turn itself back on. The sound was very muddy, which made me check it, and it was clear when I turned it off. So when the sound became muddy again I would check and, sure enough, it somehow turned itself back on.

Why is this happening? I have not yet experimented much, but all I can think of is that I loaded the scene from VSL via remote control on the iPad. The EQ must have been on in the scene. The iPad was remote was then switched to the overview tab, but then I switched apps on the iPad to control lighting and review wireless settings. I wonder if every time I switched out of the remote control app and back in, if it reloaded the scene. Does anyone know if this is an issue with remote control and scene loading? If so, does only happen when you are on the scene tab, or anytime you open the remote control app after loading a scene?

I wasn't actually running the sound, so I didn't notice if fader levels were also changed, I only noticed the EQ problem. The sound guy said he did not turn the EQs on. If you have any knowledge of this problem, please let me know how to avoid it isn't the future. I am using a Mac mini and wanting to run it without a separate monitor and keyboard, so being able to load scenes from the iPad is important.

After saving the scene with the fat channel off on both the computer and the board, I thought there was no way it would pop on again, but sure enough it continues to do in both the main and submit channels. I cannot figure out why.

I found that I can, however, save zero gain settings so that when the EQ pops on, it does not affect the sound. I wanted to save a non-zero setting, but leave it off until I used certain equipment that required it, but until Presonus fixes this, I guess I won't be able to. I still don't know what causes it, but I've done what I can to prevent it, and it still happens. I also lose connection between the host/computer application and remote control periodically, and it seems to happen then. I have verified that the connection problem is not due to the router - the app seems to freeze up at times.

I thought I had the connection problem fixed with a static ip set on the computer, but after a recent OSX update, the connection problem is back. I am not very happy with Apple lately. On both iOS and Mac they keep producing updates that cause problems for me, but I don't know for sure if it is OSX or the VSL that is causing the problem.

What you are all seeing could LIKELY be that the FAT channel selection such as INPUT, OUTPUT, SELECT of a Channel, etc, is randomly triggering. The buttons are scanned in a matrix and the panel may be switching between functions. This would require an oscilloscope and troubleshooting knowledge to isolate. The bus that samples this is fairly high impedance AND if your board has been subject to humidity there may be enough electrical leakage to trigger random behavior. If your board has been subjected to this, warm it up and place dehydrators near it for a week.
Every control except the input trims and the faders are sampled by the same matrix that is likely done by the Atmel processor on the little board by the display. The switching sample gates are all over the panel circuit board. Note that a MARGINAL power supply on the 5 volt bus could cause this, and while most other things work, the digital panel sampling may be flaky.

This type of behavior follows me ever since I purchased SL 16.4.2 (ver 1) in 2009

The unit has been in repairs several times, has been replaced once... and still is the same.
Scenes change on its own, other settings of fat ch.

I noticed that whatever SELECT button stays pressed last, those settings change on its own later.

10 years of nightmare with StudioLife.... Considering changing the mixer but it will never again be Presonus