Some of my subscriptions show an error for the actual report screenshot. When I open PowerBI the data displays properly. Other subscriptions work fine. Screenshot of the error below.
Experiencing the same issue, seem to have it narrowed down. If the subscription triggers while a refresh is in progress it will show an error like OP indicated.
It has become a major issue for me as we moved on to premium and the number of reports we have refreshing within our org has caused extended refresh times, so it is difficult to time refresh/reports properly to get up to date information without hitting this situation.
A poster higher up indicates that it is mimicing what an end user sees, but this doesn't seem to be the case as users can access the reports just fine during a refresh but a subscription will have this failure.