In the web client, prediction patterns can only be deleted if all the issues attached are in the "expected" state. Once an issue is received, the delete button becomes greyed out. I personally see it as a welcomed change. In the XUL client, deleting the prediction pattern also deleted attached issues/items. Removing the ability to delete the prediction pattern gives me less chance of accidently deleting my issues.
If you want to delete the prediction and issues, you can choose the Action "Reset Items" on the Manage Issues screen, which moves the issues back into Expected state and will allow you to then delete the prediction.
In the web client, prediction patterns can only be deleted if all the issues attached are in the "expected" state. Once an issue is received, the delete button becomes greyed out. I personally see it as a welcomed change. In the XUL client, deleting the prediction pattern also deleted attached issues/items. Removing the ability to delete the prediction pattern gives me less chance of accidently deleting my issues.
If you want to delete the prediction and issues, you can choose the Action "Reset Items" on the Manage Issues screen, which moves the issues back into Expected state and will allow you to then delete the prediction.
The bug in comment #2 sounds a lot like this one: https:/ /bugs.launchpad .net/evergreen/ +bug/1746536