This one that you describe
" The other leak appears in the same corner of the vent fan. "
Was remedied by removing the caulking around the vent fan where it mounts onto the shell and reapplying same. There are some 1 by somethings, not wood, up there that sort of make a mount for the fan assembly that sit atop the shell and under the fan. My leak was in that mounting. The water was getting in and migrating to the door side corner of the vent fan.
Regarding your front shell. Mine also slants a little toward the TV when it is set up and the TM is level. As long as the bag seals on each shell are good I would not imagine water coming in from that direction. From reading the Forum is seems like most leaks on a TM are caused by some caulking somewhere, ( thats the fun part
) that is not sticking or has cracked just a wee bit.
Good Luck!