welcome to the forum
I am not aware of any fix other than replacement of the whole assembly. It's not necessary to remove all the coroplast, just enough to gain access.
Your underbelly is most likely held on with 3/8" self tapping screws. Takes about 10 minutes to remove enough to drop the entire front portion. I have layed on the coroplast while I changed valves numerous times.
Maybe someone else has a "trick" I'm not aware of.
__________________
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.