Hi - yes this is happening to our Guest stays as well -- all the numbers (outside of what I plug in for the accommodations) are wrong on extensions for any length of time!!!! Including addition of occupancy taxes to stays that are 90 days plus and fully exempt!
I did not realize this was happening myself since I can't see the prior total for the Guest in the alteration tool; the Guest's informed me.
I have not yet been able to get any assistance regarding what is going on. I have support looking into it again. I don't see anything online relative to changes taking place. This is the first post I have found! Please let me know if you have learned anything else since posting!!