Randomly, but frequently, when I'm working in projects of any size or complexity the preview resolution will suddenly drop to a very pixelated level. It doesn't seem correlated to any particular thing I'm doing in AE, unfortunately.
If I set the preview resolution to Full, it will look something like 1/8th resolution, and at Quarter resolution it's more like 1/64th. When I hit the spacebar to play forward, the resolution jumps back to Full (if I have it set to Full) and will play as expected, but when I stop, the resolution dives again. So this is only happening when I'm not scrubbing or ram previewing, just sitting and working on a frame.
I've cleared the Database and Cache, and my (emptied) Disk Cache is set to a USB3 external SSD. The only solution so far is to quit and restart. It seems clear this is a memory problem, but I'm not sure what kind and how to resolve it.
3 GHz Intel Xeon W
64 GB 2666 MHz DDR4
Radeon Pro Vega 64 16368 MB
Ae is version 15.1.1 Build 12, but it's been happening for the past year through several updates.