2007 Crescendo shower leak

[Johnny Boy]

I have the Crescendo 8386 and recently i noticed when using the shower there is water dripping from what appears to be a small box structure at the top of the drivers side rear wheel well, It doesnt leak when using the bathroom sink or the kitchen sink- only when using the shower. I looked thru the access panel in the batterom shower base and no water leaking from drain area or pipes going thru the shower floor, so leak must be happened under the wooden floor to the grey tank ? here are some pics where its dripping from. The small box appears to have screws holing it up and hinged on 1 side anyone seen this before?
Please help if you can going on trip soon and dont want any problems