Hmm, the change to the save format should only affect old save games, they should not affect new save games.
I've used save games multiple times with the new version, and just now actually, and it seems to be working.
I do know there are some problems if loading and saving on OLD Microsoft edge (the non chromium edition). Can you confirm you are not using that release?
If so, please upgrade. My understanding is the Microsoft is forcing all Edge users onto the new Chromium version of Edge soon.