Most likely your server responses aren't correct. Did you read the Store API docs? Do you have a test case showing your problem?
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We have a further check while deleting a task in rest. For example, if a task has a progress it cannot be deleted. Exact error message is sent as the response while syncing the store after deletion based on which we have used undoAll functionality of UndoManger. Later if some-other task is edited and then while syncing the store there is a post call happening for the earlier task which is already present in database and so we are duplicate error as the response.
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Pavel Miklashevich - Core Developer
You need to keep you data consistent. After a request, please reject your changes in the stores (in case of failure), or commit changes (is case of success). If you are using crudmanager please be careful since it handles different stores. If you're using undo manager it's better to call undoAll to revert changes, and clearQueues on save. If you'll need a further assistance please submit a runnable test case that shows the issue. Cheers!
Pavel Miklashevich - Core Developer