If it were me, I would consider finding an expert tile guy. Tile can be an art, especially when you've got to remove individual tiles. Although a tile guy would probably not be covered by the warranty.
take it out of the shop and let a real tile guy look at it... RV dealers are NOT tile people...
I would suspect that because it is tile, is ONE if not the main reason it has taken 5 months to get it done, because they don't know what they are doing...
maybe you could get some reimbursement from FR