2.1 Update: Migrate dashlets - KeyError: 'timerange'

CMK version: 2.1.0p3
OS version: Ubuntu 20.04

Error message:
-| 11/25 Migrate dashlets…
-| + “Migrate dashlets” failed
-| Traceback (most recent call last):
-| File “/omd/sites/test/lib/python3/cmk/update_config.py”, line 238, in run
-| step_func()
-| File “/omd/sites/test/lib/python3/cmk/update_config.py”, line 1217, in _migrate_dashlets
-| transform_timerange_dashlet(dashlet)
-| File “/omd/sites/test/lib/python3/cmk/gui/plugins/dashboard/utils.py”, line 944, in transform_timerange_dashlet
-| }.get(dashlet_spec[“timerange”], dashlet_spec[“timerange”])
-| KeyError: 'timerange’

while trying an update from 2.0p21 to the lates 2.1p3, I receive the message shown.
Can someone explain how to fix that ?

glad to read your answers,
br Marco

@_rb was able to help me.
with a “print(owner, _name)” inside ~/lib/python3/cmk/update_config.py in line 1217 I was able to get the faulty dashboard and fix it.