I just saw your post today...we do not have a 5th wheel, but, was concerned about your situation. Our first motorhome was an older model...we had no issues, other than old carpet,which my husband pulled up after a couple years and put down 'self sticking' tile. Perhaps, if you are handy, you can pull up the bathroom floor...access your problem and fix it, or get a handyman to do the job.
Good luck and keep me posted on your experience
Ron & Kay n KC too !
2001 Scamp 13'
'KC's Little Box'
Jeep Wrangler TJ