I have a huge, huge session in S1 4.5 that was working fine until I reinstalled Windows. I went through and did as much of the optimization stuff as I could find, but my during playback (even while it's just sitting here, honestly, I can hear something quietly humming in the background that is also dropping out) some instruments will drop out for just a second or so then come back. When they drop, the meter drops, too. I'm fairly sure it's an optimization setting that I'm forgetting, but it's been a couple days and I can't seem to find it.
Windows 10 10.0.18362, build 18362
Studio One 126.96.36.199232
S1 installed and running from Samsung 960 Pro NVMe
UAD Apollo Twin MkII + Satellite, driver version 9.10.1