My ex also runs hot and cold and I've largely just ignored it. I am pretty much NC aside from the kids. We have had some more communications recently to sort out the S and D legal processes. About the WAW question, I agree with what LH, J, and AS have said. Even if there were legitimate reasons of not being valued in the MR etc for the WAW leaving, they also contributed to that dynamic in some way. It is not the LBS's fault 100%. So, I would need to see the WAW take accountability of what they did to bring the MR to where it degraded, and also remorse and contrition about the way they went about it - BD and that abrupt severing of the relationship. There were other options that could've been pursued but were never entertained.
My prime thing is that both sides need to take accountability. With a WW, there's more to the story for sure. But without that accountability and humility, there's nothing to entertain.