MikroTik hAP AC Lite - VLAN questions/problems

Hi,

last week, by mistake one of my colleagues removed the LAN VLAN 1 from his hAP AC Lite settings. After that, he couldn't access the hAP anymore, so he gave it to me to check. I could access it through the WAN port, went to the settings and added the LAN VLAN 1 again. Now the confusion started:
 

• When adding the LAN VLAN 1, this setting was never saved. Next time I checked, the field sayed "untagged" again. I've tried that several times, without success.
• Adding LAN VLAN 5 for example worked without problems...but reverting back to VLAN 1 didn't.
• After a reset of the hAP, the LAN VLAN 1 was automatically set again - what leads to another question...
• ...why is it set for LAN VLAN at all? according to the documentation: by default the WAN uses VLAN 1 and the LAN is Untagged on single port devices. 

The LAN ports are accessible again after the reset, but I really don't understand what's happening here...is there something mixed up in the firmware?

Thanks
73s de Kurt HB9XCL