I had a hairline crack in the shower pan of one of my earlier rv's that only opened and leaked when someone was standing in the shower. Fixed that with some Eternabond tape.
Also, had a leak in the shower drain pipe on the Vegas this past year. The trap was resting on the floor under the pan and cracked the connecting pipe fitting from the tailpiece to the trap. Fixed that leak with a rubber sleeve available at plumbing supply. The Vegas leak dripped out of the rear wheel well due to the angle of my driveway.
You probably have a different shower than the Vegas, but most likely are have the same leak prone areas.
You probably have an access panel on or near the shower pan you can remove and check for leaks.
2015 Thor Vegas 24.1 in Ocala