Make sure to make manual backup of your Planet Coaster files, such as your saved parks, blueprints, TMT items and custom media (music, billboard images and videos).
In the event that files get deleted due to this issue, you can restore them with this backup.
PS. I haven't updated the list with the location of TMT items but as long as you're subscribed to TMT items from others you should be able to get them back as long as they are still available on the workshop.
Location of local Planet Coaster game files
Saved parks, blueprints and campaign progress
"%userprofile%\Saved Games\Frontier Developments\Planet Coaster\12345678901234567\Saves"