Hi Robert,

Yes, they are all the loops that are included with Studio One Pro.
In those, there's all the effects, chord progressions, and single shots.

PreSonus also offered some loops from a company called "Nine Volt Guitars" which were added a few years ago... in there.
I've only added some thunder and rain loops myself into my soundset folder.

So to be clear, I used to be able to just drag and drop loops from those soundsets located on my external USB 3.0 1TB Western Digital drive (via the S1 browser) into my song and they always worked. I usually left them 'as is' and only bounced a few but not in every song, so I cound transpose, etc..

I had a couple songs to finish in 3.5.6 so after that, I upgraded to 4.0.1 and that's when the issues immediately started. I found the only way I could keep using the soundset files from my externnal USB 3.0 drive was to always bounce them. But now that I've moved them all to my internal SSD drive, I can once again leave them in their most virgin state. This I do so that I can only manipulate them if needed - cuz if I bounce here and there and make edits weeks into a song, I'm commited.

And yes I understand that if I load a bunch of "Instruments" that could cause performance issues or audio dropouts but the songs that exhibited this when I first started using 4.0.1 were very simple and short arrangements. I've since removed the folder containing my test songs and files since I've resolved this issue for myself... but it doesn't answer the question as to what PreSonus changed in version 4 that now causes this?

Scott