Rotobrush 3 (beta) not working as expected

I am VERY VERY new to AE and teaching myself, so forgive any 'dumb' questions. I'm trying to teach myself rotobrush 3 (in AE beta) and so far I've been very successful. Even on the same shoot, where almost all environmental elements are the same, everything renders great and as expected. For example, in the photo here, this shirt is normally not a problem. However, suddenly, on this one particular set of images, where lighting was only slightly different on the images, rotobrush no longer works as expected. I'm not sure if this is a "bug" or something I'm doing wrong with the propogation method. I left it the same for all items, it just suddenly didn't like these. What's weird is that in the composition, IT SHOWS CORRECTLY. It is ONLY on the render that you can see the mistakes it made. Complicated story, but do to my slow machine, I render to Quicktime format with the video output using RGB+alpha. Again, this method proved super successful in many prior attempts but suddenly, what you see is NOT what you get in the rendered product. And once it started to do this, it continues to do this. I'm doing more shots today, and will try another busy shirt. I played around with all the propagation variables and non really helped. Again, not familiar with AE much at all, but learning as I go. Does anyone think it's a bug since literally you cannot tell there is anything wrong because the layer and composition show up perfectly, it's only on export that the errors occur. (BTW, I did try and just use the .aep project in my premiere file instead of the quicktime file, but same result.