I just updated Monday (same version both CMK and OS) and see the ame problem.
2025-11-05 06:49:54,651 [20] [cmk.base.notify] Replaying notification 0 from backlog… 2025-11-05 06:49:54,651 [20] [cmk.base.events] Error on completing raw context: ‘SITEOFHOST’ 2025-11-05 06:49:54,651 [20] [cmk.base.notify] ---------------------------------------------------------------------- 2025-11-05 06:49:54,651 [20] [cmk.base.notify] Analysing notification (;File C:\Temp\FILENAME.csv) context with 54 variables 2025-11-05 06:49:54,651 [40] [cmk.base.notify] ERROR: Traceback (most recent call last): File “/omd/sites/monitoring/lib/python3/cmk/base/notify.py”, line 493, in locally_deliver_raw_context return notify_rulebased( ^^^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/notify.py”, line 763, in notify_rulebased why_not = rbn_match_rule( ^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/notify.py”, line 1216, in rbn_match_rule return events.apply_matchers( ^^^^^^^^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/events.py”, line 490, in apply_matchers result = matcher(rule, context, analyse, all_timeperiods) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/notify.py”, line 1219, in lambda rule, context, analyse, all_timeperiods: events.event_match_rule( ^^^^^^^^^^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/events.py”, line 503, in event_match_rule return apply_matchers( ^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/events.py”, line 490, in apply_matchers result = matcher(rule, context, analyse, all_timeperiods) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/events.py”, line 509, in lambda rule, context, analyse, all_timeperiods: event_match_servicegroups_fixed( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/events.py”, line 634, in event_match_servicegroups_fixed return _event_match_servicegroups( ^^^^^^^^^^^^^^^^^^^^^^^^^^^ File “/omd/sites/monitoring/lib/python3/cmk/base/events.py”, line 664, in _event_match_servicegroups if context[“WHAT”] != “SERVICE”: ~~~~~~~^^^^^^^^ KeyError: ‘WHAT’