Very possible. The AC unit is held in place by 4 screws that pull the unit down onto the roof and compress a foam gasket. Over time the screws can get loose and/or the gasket can degrade.
Remove the ceiling plenum, and the air diverter. You should see a long screw at each corner of the opening. Try tightening them, and then do another water test.
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.