we recently got a problem where we are not able to delete, edit or export analytic rules due to a [object object] error. See image:
After extensive contact with the Microsoft Sentinel product team, we found out that this problem is caused by having a "&" sign inside the rule id or rule name. We notice that several analytic rules have the "&" sign in their template. For example the F&O rules of the in-preview Dynamics dataconnector. Creating a rule manually will validate if the & sign is present, but since we deployed these analytic rules via our deployment pipeline in an arm template this was not the case.
The only solution at the moment is to contact microsoft support and provide them the rules so that they can delete the rules manually.
We hope you found this post usefull and give you the solution to this problem.