Hey,
I had this problem, I put a baneling model to a probe and it can't gather now...
Any ideas why this happen? and how to fix it
Thanks

In order to gather a unit needs a gather ability. Check the abilities on the unit to see if it still has gather.

Temp, I just changed the probe's model. It's still a probe, so SHOULD be able to gather, as it's able to build.

I've tested changing a probe's model to a baneling and gathering still works. You don't see the minerals on them after they finish mining but they can return it to a nexus just fine. This is because the attachment point used does not work for the baneling (It does not have a hard point attachment). You can fix is by changing the attachment point for the carry resource actors to the head (not sure how this will look on actual workers).