Ive had similar problems like this before so finally time to sort this out. Im on the latest version CC 2105 too.
Im on quite a complicated project but will simplify my problem. If I mask out shapes from live action inside a pre comp, then in the main comp use time remapping. The masks slips from the footage.
I have a ton of composited shots in AE and now need to time remap the whole sequence as the final change yeah it renders with loads of errors. My sign replacements are off, masks slipping etc etc. They are fine in the pre-comp at normal speed.
Do I have to render it all flat before I time remap as I really would like to keep it editable.
Your Vimeo link appears to be broken.
I am trying to understand whats going on here. it sounds as if the masks are not effected by time remapping and so when you remap everything else it's animation is off a bit. If the masks ON the composition you are trying to remap and not inside of it then that makes sense. you would need to precompose it and remap that but if it's not then I'm not really sure.
Sorry that link must of been an old signature. Its not related to my question.
Ive tried different pre-comping options but still end up with the same effect. Some comps are over 10 precomps deep but the master comp never remaps it properly. I can get round it by pre rendeing but its ads time in my workflow when making changes. Im guessing its another 2015 bug.