Dear friend we have that issue too with tmdhosting!
What we noticed:
It’s happening everyday at a particular time. It lasts for about 40 minutes. And then everything it’s working again.
During that time that the problem occurs you can’t customize the theme. Any theme at any site if you have at your package – let’s say – 6 sites.
So far we haven’t found a solution. Error logs are clear!
Just to know and if you want to refer to us at your problem at technical support our ticket is #925131
Thanks!