The metal seals on my axle bearings end up coming out and just hang on the axle after almost every session. I would assume this is not normal?
Yes, That Isn’t normal.
how old are the bearings? does it happen to all 3? By the looks of it and your description of them popping out after almost session, I would either put it down to the ring being bent/damaged or the bearing race being distorted. After constantly popping out and being put back in, the ring will likely have bent a little. Also, a lot of grit is has been introduced when the ring comes off which is not only damaging the bearing itself but also likely causes the ring to sit unevenly in the bearing race. I am not familiar with Top Kart, do they sell the bearing ring/seal separately? I would spray the bearing out with some brake cleaner (be careful of the cleaner hitting the chassis to prevent the paint from being eaten) re lube the bearing internally after this. I would also clean the ring and sort of hammer it back in to where it sits tightly in the bearing.
However, if you could I would replace that bearing as well as the others as preventative maintenance, I suspect the one in question is on its way out anyway. Bearings tend to wear out prematurely when being introduced to grime and water, its not abnormal to have to replace them once or twice in a season. Investing in some fresh ones now can save a lot of headaches on a race weekend and keep you out longer in practice.