I have been experiencing playback and buffering issues for months with all my UHD purchased content through the Movies&TV app with no fix in sight. I have requested refunds for many of them since $30 is an outrageous price to pay per film when other providers offer them at half the price with no playback issues.
I cannot continue to purchase content through Movies&TV as long as the servers cannot handle the playback load. This does happen more frequently during peak times as already stated and it is ridiculous it has gone on this long.
And it is still going on several months later. Thanks for not fixing the issue Microsoft.