Bizarre cause of shower screen sticking

A big plus of the Kemerton XL is it having a separate shower cubicle opposite the WC in the rear bathroom. The shower has two sliding doors which meet in the middle but from new one of our sliding doors would stick when opening. It's been enough for me to start wondering nay fearing that one day I might not get out!
We've been away this weekend at the Warner's Peterborough show and with Covid we've been having showers every night, so finally I got around to having a close look, why was one sliding door sticking. It seemed that at floor level A-S had added a short 10cm of track that has the end stop. Either sliding door can close up in the middle to the end stop and not be able to go on any further.
I concluded that there was probably something of a misalignment between the track and the short length that has the end stop, surely that's why it was sticking. Back home today I have another close look at floor level and it looked reasonably OK, not enough to cause the problem we were having.
Looking above me at the top track I see a clear plastic dome shaped bump stop jambed between the shower surround and the track, somewhat distorting the alignment of the track. With a kitchen knife I lever out this bump stop and the sliding door behaves normally with no sticking. Heaven knows how it came to be there. Did someone in manufacturing put it there or did it happen by accident? I cannot see a reason for a clear plastic bump stop being there.

So far both sliding shower doors work normally with no sticking so hopefully no more anxiety when having a shower!