Unfortunately, there was a serious error found in the micro-controller code. It is highly recommended that anyone who has flashed their micro-controller code between Oct 27th and today update their code to the latest version and reflash all their micro-controllers (commits 7d95a004…9ecddd1b are impacted). Users on the v0.10.0 stable release are not impacted by this and can remain on that release.
The #4832 commit made a change to the low-level “scheduling” code that was not complete. In some rare circumstances this could result in the scheduler not working correctly. In particular, it would be possible for code that is designed to run at a regular time interval to not get scheduled properly. A fix for this issue was made earlier today (in commit 9ecddd1b).
This recurring schedule mechanism is used internally by several safety systems in Klipper. It is thought to be possible that the above code defect could result in the safety checks not running properly. It is therefore recommended that impacted users update to the latest code and reflash all micro-controllers.