Search YouTube for stuttering or micro-stuttering (two somewhat different symptoms). It’s basically the game freezing for what is almost an imperceptible amount of time but usually very frequent and with a pattern (micro-stutters) or for a few seconds, normally due to the game engine loading something or badly managing CPU threads, this can happen seemingly at random.
After patch 5 I started getting long freezes, maybe up to 3 or 4 seconds which I thought were almost CTDs (crashes to Windows’ desktop). Patch 6 made those long stutters/freezes actually trigger a CTD now, so it’s worse for me.
You can use this trick to figure out what’s going on: Open Windows Task Manager and make it “always on top”, go to the “Performance” tab and double click on any graph, that will give you a slimmed down version of Task Manager. Now open FS2020 and fly around. Keep an eye on the CPU, Disk, Memory, GPU usage when the stutters happen. With 16Gb of memory and playing in 4k I would suspect you are at about half the memory you actually need.