We're experiencing an issue with a number of Sites in SharePoint Online where by the Master Page inheritance stop working and the page looks like the image below. To fix it I need to apply a theme which brings back functionality, and then set the site to Inherit, and then the site returns as normal. However, it breaks again not long thereafter. It's broken 4 times in the last 12 hours. Has anyone experienced this or know why this is failing?
Assistance is greatly appreciated.