Black water tank leak at top where pipe connects

[Shounshell]

Our 2007 Sandpiper 5th wheel toy hauler is leaking around the top on the black tank and we are suspicious it is some how failed at the top portion or come loose or the supposed rubber grommet has failed where the ABS pipe connects from the toilet. Looking for answers before "digging in". We are on a winter assignment and cannot move it. Unfortunately for us it is not a straight shot for the toilet to the tank it has "2" 45 angles to the tank! What is the best way? And do you know if FR did glue these around this time or use the grommets? Another question anyone have a best guess if I pull the toilet and flange can I get that S shape out of there from the top and see and fix that issue from the top perhaps?? Worried like crazy in Northern New Mexico Right now.. Ps. My husband can usually fix anything but trying to figure out the best way and where to get our parts... Help appreciated.