No alert due to maintenance window although not set

[cybermcm]

Just trying my first steps with librenms and now discovered a problem beyond my knowledge.
Setup:
latest docker container with librenms_dispatcher and librenms (and all other stuff like sql,…)

Setting up my first target and monitoring http for example → all working
Disabling http for testing on target host → alert gets created → email gets send

Now I want to add a recurring maintenance window for the night (lab host, I don’t want any alarm during the night, starting at 10pm and ending at 06am, see screenshot).

Although both time windows have only the “set” tag, no alarm is created during daytime…
If I delete the “night2” window, alerts are working again.

Am I doing something wrong? Maybe I haven’t understood the maintenance setup correctly?
Any help appreciated…

[cybermcm]

I’ll follow up here…
I tested further and discovered that there is a strange bevahiour…
If I set a maintenance windows from 00:00 to 00:59, everything works (no maintenance icon in the device list)
If I set a window from 02:00 to 06:00 everything OK (no icon)
As soon as I set something with 01:xx, e.g. from 01:00 to 01:01 or from 00:59 to 02:30 the maintenance icon appears and alerts are not working…

any ideas?