Have you tried to deactivate with the WEB-UI or the App/Cloud?
Edit just disable and update don't reboot when disable it
Yes, I updated my post too, but you just are to fast! 
Changing the setting through the WEB-UI does work. My FW's are updated now.
Silly this has such an impact. Never the less, glad it is solved.
@ Everyone for whom the update cannot be carried out: please deactivate WiFi backup and update again. Should then work
There must be a relation between the settings, both my devices have WiFi backup enabled with no settings entered. Can't remember enabling them but can't disable them either. When I clear the checkmark it tells me 'backup wifi set successfully'. But after rebooting it is enabled again.
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Disabling through the webpage does work. Updating now to see if it works. -> Yes, works!
I saw Demitri on Facebook also investigating the same issue. I guess it is a more common issue
doesn't change anything. The same thing. It says 'updating' and then nothing.
can you share your OTA-Link for an example please?
The link i'm getting:
http://192.168.0.15/ota?url=http:/…SW-PM_build.zip
The reply i'm getting
{"status":"updating","has_update":false,"new_version":"20210727-202339/v1.11.2-g25b6953","old_version":"20210429-101828/v1.10.4-g3f94cd7"}Okay, is there anything else with those who can't update? Tried over fixed IP? Internet connection available?
Nope, all of them I have been using for like a year or so. Some a month older. All have exactly the same internet connection, same wifi, all have fixed IP's. Nothing I can figure out what goes wrong.
welcome to the forum,
have you already tried this?:
Yes, that's what I tried at option 3. My apologies for being unclear. When I past the URL it doesn't do anything. It shows me the 'old' fw inline so I know it is connected to the correct IP, but after a while it ends up with the same thing. It stays at 1.10.4
I have a couple of 1PM's stuck at firmware 1.10.4. For some reason they don't want to update to 1.11.x, now 1.11.2 just got released and again these 1PM's don't want to update. Various other 1PM's are updating to the latest version.
What I've tried:
1. Firmware upgrade from SmartPhone app.
2. Firmware upgrade through webpage (accecced by IP)
3. Try to use the support site to update the firmware
4. Rebooted prior to upgrade firmware
5. Disable cloud, try and upgrade, reconnect cloud (as suggested per facebook post)
6. Physically detach the L wire and try all above.
Nothing seems to work.
Any advice?