Let's Encrypt did enable something (for a very short time period of just 8 hours) that every ACME client should be capable of handeling (Enabling Asynchronous Order Finalization). However, enabling asynchronous finalization on the production environment was postponed indefinitely due to too many broken ACME clients. And it was enabled not too long ago by accident, but only for a few hours I believe.
Other than that, I'm not familiar with any change that could have impacted your auto-renewal. I don't believe the asynchronous order finalization stuff I mentioned above would stop auto-renewal permanently. If DSM couldn't handle that, it would only have failed once or twice at most, but should have succeeded afterwards again when asynchronous order finalization was disabled again.