The problem is that the factory isn't/wasn't using enough glue under that disc. It happened on the last batch and I reported it. It happened again on this new batch and I reported it. I'm hoping the factory actually starts paying attention to this important request.
When (if) they come off due to an almost lack of glue, I just put another dab in and quickly rub it around the flat surface then stick it back on the nub. It felt fine and that original glue dot was so small that it didn't make much of a bump anyway. Once Krazy glued back on, you'll never break it off again. The disc would be shattered before you would get that off again. If you are worried about the glue dot, maybe try to remove it but be careful. Personally, I'd just put another small drop in and spread it around the original dot.