Thanks for the suggestion! I tried it out in poser, experimenting with various weld tolerances, even regrouping the thumb 2 group (the group that just doesn't want to move) with thumb 1 and welding it and, when that didn't work, regrouping it with thumb 3, then welding it, but it still misbehaves. Is there some other way to weld/attach the misbehaving group other than through the group tool?

Thank you for your help and any future advice!

TheKeeper