Hi @dgcooper - sorry for the delay on a response!
At this time, there is no way to unmerge an automatic merge. Support cannot make this change either.
One of our earlier updates this year should be reducing the number of erroneous auto-combines, which can happen when Sense evolves the device model due to some level of correlation between the two devices’ behavior or usage (not a data scientist, though, so this methodology could be off slightly.)
We are tracking this issue as we see it, though. Have you already submitted a support ticket so we can track this issue?