Using 2.6.5 on OS X Yosemite I've now encountered several times that the waveform graphics are redrawn when I open a recent project.

I'm quite new to the OS X platform so I have no prior experience of how it 'used to look'.

This doesn't happen all the time but quite frequently. This is mostly noticeable on live multitrack recordings where I have several hours to digest and this takes a lot of time, disk and cpu to render and I've found no way how to stop this rendering from happening.

Any clue to as why this is happening? Is it possible to turn off the waveform graphics in the meantime?