Our new trailer has a shower very similar to your pix and did this also. It would fill up the lip just outside the base of the shower trim and eventually overflow.
I did extensive internet research and found several places suggesting you caulk the VERTICAL seams of the translucent panels. I did this on the inside of my shower with clear silicon caulk and it fixed our problem.
PS - some water is going to get into that channel anyway between the trim and outside base of the shower. If we are unlevel side to side, the water will stack on the low side and run over anyway. But if we are level enough for the shower door to not move when you open it half way and let go (our gold standard for levelness), then no wet spots on the floor.