Hell's Teeth: I've, always, ALWAYS been using Display ALL Frames on the Timeline. I've just "learnt" to see the frames in my Narrative and Cut accordingly. Yeah, maybe sluggish, maybe some whiteouts, and so on. However, I just completed a Project using BORIS Particle Illusion and masses of other stuff, and, after several cliches and hitches, I decided to use the OPTION for NONE. Difference? Night and DAY!!! - Very solid and reliable VEGASPRO17.
Maybe you should try this IF you're getting similar "issues" using ALL Frames Showing Option.
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