Today I received an error when trying to clone test plans in Azure DevOps web portal. Steps:
In Visual Studio, I select the Test Case option
I find the Test Plan I want to clone, select it , and then select the "Clone test plan" button.
In the "Clone Test Plan" window, accept all defaults and click Clone.
Result: an error is received: "Clone operation encountered a WorkItem Tracking error while processing test case xxxx. Retry the operation. Error details: TF51535: Cannot find field 25."
It is extremely unfortunate that this issue happened today while I am trying to clone a large test plan. I will have to manually copy the hundreds of tests in order to have the new test plan ready for Monday morning.