Poly Vinyl VS Hot Mopped Shower Pan

I am finishing a remodel and have a shower upstairs and down. I tested initially and both held water. Six months later in the remodel I am planning for tile and go to test again, after already having cut the material out of the drain. A buddy of mine who is a drain guy blew up balloons in the line to test and tells me the downstairs drain should be replaced. So there goes the shower pan, not to speak of saw cutting the slab, etc. I will have to redo the shower pan. Should I go with the same 40 year polyvinyl floor or hot mop? Also, as long as I have the guy up there, should I eat the initial investment and have him redo both showers hot mop. I notice the corners of the vinyl pan where it is reinforced with patch like material is slightly separated from the pan. Don't know if this is normal or not. Not sure what to do. Adivice appreciated. Thanks.
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