.... low humming noise and it also vibrates.......belches exhaust back into the rv through the vents
RV furnaces are sealed units......combustion side is separate and sealed from room air side.
You should not operate that furnace again until it has been pulled, inspected and repaired or replaced.
Belching exhaust into room side (thru registers) is allowing combustion by-products into inside of RV.
Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect.
THAT IS DANGEROUS and can KILL