Failed to Edit Periodic Smart Test Long schedule in WebUI

When I tried edit the Periodic S.M.A.R.T. Tests (LONG) schedule, it failed with the following error, no matter what schedule I have chosen:

# errorVALIDATION

[EINVAL] smart_test_update.data.schedule: A SHORT test already runs at Day 9th of every month, 00:00
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/middlewared/main.py", line 211, in call_method
    result = await self.middleware.call_with_audit(message['method'], serviceobj, methodobj, params, self)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/middlewared/main.py", line 1529, in call_with_audit
    result = await self._call(method, serviceobj, methodobj, params, app=app,
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/middlewared/main.py", line 1460, in _call
    return await methodobj(*prepared_call.args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/middlewared/service/crud_service.py", line 240, in update
    return await self.middleware._call(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/middlewared/main.py", line 1460, in _call
    return await methodobj(*prepared_call.args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/middlewared/service/crud_service.py", line 261, in nf
    rv = await func(*args, **kwargs)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/middlewared/schema/processor.py", line 179, in nf
    return await func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/middlewared/schema/processor.py", line 49, in nf
    res = await f(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/middlewared/plugins/smart.py", line 423, in do_update
    verrors.check()
  File "/usr/lib/python3/dist-packages/middlewared/service_exception.py", line 72, in check
    raise self
middlewared.service_exception.ValidationErrors: [EINVAL] smart_test_update.data.schedule: A SHORT test already runs at Day 9th of every month, 00:00