The one item that cross references to both of these problems is the
direct/reverse clutch plates and discs, have they not been replaced? Or are
they not properly adjusted? either way bad news this is a simple and
mandatory task when replacing piston seals and at the very least the disc's
in this clutch pack!  Also there are no valves to drain automatic fluid out
of the differential fluid only 2 seals that should be replaced!
If one of these transmission's is mixing fluid you have to pull the entire
trans out and replace these seals and at that point you probably should
spring for a new or rebuilt convertor.  I at one time would simply clean them
but unless you know for sure the age of your convertor these parts have been
in use for a long time now typically.
I hate to tell you to forget these guys but some times you have to cut your
losses
Good luck
Jeff