Originally Posted by
cseeman
It would seem that it's system related.
I assume this is only impacting the interface and not the stream. That might indicate some background task but it's hard to figure out what.
Some things to look at are RAM, available vs use of VRAM. Sometimes other applications don't let go of RAM or lots of VRAM is used when the drive is low on space resulting in slow access. One can see this to some extent looking at RAM use at the bottom of Activity Monitor where the total system stats are displayed.