Hi ArcGIS online team, @pheede-esri ,
We just ran into a very frustrating issue with ArcGIS Online.
Our users were attempting to apply edits via the editor widget in Web AppBuilder. They have to use this tool as they are splitting polylines, and it is the only one that functions in the way they need.
Anyway, their edits were not applying, with no reason returned to the user. The users were getting very upset with the platform and losing confidence in ArcGIS Online products. It was also only happening to some features and not others.
Using Chrome devtools I worked out that the issue was poorly formed data in a different field that was preventing the edits from being applied:

Please please please provide some user feedback when things do not work!! Yes the data was bad, but having to dig into devtools to debug simple editing issues is beyond the capabilities of many users, and also not what we would expect of an "enterprise" product.
Thanks,
Marc