It's been my experience that if you have root rot, repotting in a larger pot will just make it worse as the pathogens are still on the root ball and spread into the new soil that holds more moisture than the old one, so seeing if the roots are rotten can help. But yep as long as the corm is solid it can be saved, basically its like a bulb. Any I have that dont have roots from rot, black, etc. (And hot sun will kill the roots sometimes as well when it heats up the pot) I pot them up in pure Sphagnum moss which is antifungal, antibacterial, and airy, and keep them damp until they regrow roots. Even with the dampness of the sphagnum, the anti pathogen qualities of it usually reverse the issue. I have saved a few plants this way, that normally would keep getting worse till they died. Winter can be tricky to get plants through, sometimes it seems as maybe the soil is full of some pathogen and just a bit too much water kills them, but those definitely need bigger pots soon,and I suspect that's the culprit, my adult dwarfs are in about a 10 gallon pot. Here is a Musa High Color mini pup that actually did have root rot, half the corm was soft and rotted also, the leaves were totally dead and withered not too long ago. Now after gently cleaning off the dead matter, cutting off the rot, potting up in pure sphagnum, and giving it a few weeks, it is ready to repot in soil.
