This has been an issue before. Example - Navigation: loading custom waypoints from .pln files is broken on some systems Make note of Navigraph’s reply at the bottom.
Seeing that Navigraph had dealt with this sort of issue, hopefully they can get us an updated AIRAC soon. It’s been brought up on their forum.
I’d just sit tight and not uninstall any of today’s MSFS updates but perhaps just disable for now, the navdata folders when flying any msfs plans made pre-WU12.