Shelly 2.5 will not downgrade from 1.9.3 to 1.8.3

I had a problem also to downgrade a Shelly 2.5 to FW 1.8.3 with the url ota method ip/ota?.... linked to the firmware archive.
(had this done without any problem several times before on other Shellys )

Got it finally, with a solution i dont understand.
My configuration FB 7560 , AVM Repeater 600 (Mesh), Medion Powerline wlan.

The Shelly with downgrade problems was always connected to the repeater and i was not able to ota downgrade it.

Finally i disconnected the Shelly from the repeater and connected it to the powerline wlan. The downgrade worked afterwards.(Maybe it worked also if i was able to connect it directly to the FB)
So it seems there are some problems to make the ota process work if the Shelly is connected to the repeater in my configuration.
Maybe there is some missconfiguration in my setup.

So it is maybe worth a try to have the Shelly not connected through a repeater for problems with url ota up/downgrading.

I experience the same problem on one SH2.5:
After stability issues with 1.11.8 i wanted to downgrade tio 1.11.7 and this wwith several tries, several browser, restrict login disabled, ....
Does not work
URL
http://192.168.178.85/ota?url=http:/…1.7/SHSW-25.zip

Result:

status "updating"

has_update false

new_version "20220209-093016/v1.11.8-g8c7bb8d"

old_version "20220209-093016/v1.11.8-g8c7bb8d"

Any idea whats the problem?
Thanks
Aare