Guessing this broken update just got pushed to the LTS channel as I'm starting to have users affected by this today.
So far any system with this update has all macro containing documents opened from the network share open instead from INetCashe. I have tried everything related to network shares in this thread and either the workstations were already setup that way or there was no effect.
Adding the network share to trust center does nothing, it already was there.
Use name instead of IP for network share. No effect, share is already by name.
Add fileserver to trusted sites. No effect, was already on the list.
Remove custom addons. Only had Dymo Label and and removing it had no affect (other than breaking label printing).
Uninstalling and reisntalling Office worked, until Office updated, then it was broken again.
It looks like the only fix for me is to reinstall an older build of Office and disable updates...
Edit: Disabling updates via the option within Office didn't work overnight. Users came in the next morning and were unable to work again. Will have to find another means of blocking Office from updating another workaround to this bug can be found (do not have hope the MS will actually fix it when Office is full of 25+ year old bugs).