Disclaimer: Guy I know installed a stand alone fiberglass pan shower.
Problem: The existing drain was off by 1/4" so he shifted the drain adapter on the pan to line up with the pipe no water puddles near the drain because it isn't seated properly.
Difficulties: Bathroom is completely finished - tiled, painted, accessories, bath mats, etc. Slab construction - no access to underside from basement. Finished room on the back side of shower.
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