Sloped roof tiles disappear

Game mode: Online
Problem: Bug
Region: Europe

Every morning when I log in sloped roof tiles have just disappeared from my tower. It’s every other tile all the way round. If I rebuild them they will remain in place. Logged off after 11 last night to make sure no one was destroying them. (though it would be odd that it was done symmetrically all the way round) logged in this morning and all have disappeared again.