So, yes, this is a hotly debated issue and no one has any answers besides workarounds and it is very frustrating.
The problem is that there occasionally happens to be ONE FRAME of render that has multiple lines missing for no apparent reason. Most folks say “YOU DON’T HAVE THE RAM SPACE!” or “CLEAR YOUR CACHE” and those would both be great ideas, if they worked. But, they don’t.
The real issue has nothing to do with RAM. Well, not really.
If you go to your AE timeline and find that one frame that is just like it is in your render. That is the problem. The render isn’t the issue, since the clip in the timeline clearly has the same glitch.
I was able to eliminate the error by duplicating the defected layer and deleting the old layer. The DUPLICATE LAYER WILL BE ERROR FREE.
So, yes it does have to do with the RAM rendering the effect or clip, but clearing the RAM will do nothing since the bad render has somehow been burned in.
BAM.