Video plays fine in Windows player. Seems Vegas is doing some kind of conversion. But I thought V16 supported HEVC. This file is .MOV and has 48mb/s data rate.

With project at 60 fps, playback slows to about 30fps within a second. Then, in either 60 or 30fps project (with resample disabled of course) rate drops to 1.5 within 22 seconds.

Doesn't matter if project is set to UHD or HD1080. Nor if preview is at BEST or PREVIEW.

My GPU is AMD Fury x. CPU is threadripper 1950 x.

I paid $0.99 to download the Windows HEVC support. But it didn't make a difference, and Windows player was fine before.