Default firmware version restored after several shutdown/reboot?

Hello,
I observe an undesired phenomon on our AXC F 2152 PLCs on which were initially updated with 2023.0.7 LTS firmware :
Firmware version has been restored to the default one : 2022.0.4. This without any action done on webpages.
I made some tests and it seems when several consecutive reboot/shutdown happens during plc restart sequence, it forces old firmware version to be restored. Do you confirm it is nominal behaviour from PLC ?

The undesired consequences of this firmware change (back to 2022 version) are :

                1. OPCUA server Global space index differs from one firmware version to the other .. Indeeed namespace index of PLCnext>Arp.Plc.Eclr in which are exposed all program nodes is 6 for 2023.0.7 LTS firmware whereas it is 5 for 2022.0.4 default firmware. Same question : is it known behaviour ?
                2. No more access to cockpit tab on webpage (whereas we have it with 2023 firmware). Is it a known evolution between both firmwares ?

As a consequence, change of firmware is a real issue for our client applications. Is there a way to prevent this firmware version restore ? Or is it possible to set a new firmware version (here 2023.0.7 LTS) as default firmware in PLCs ? So that when there happens electrical troubles, PLCs do not restart with an unknown or undesired firmware version.
Thanks

Do you confirm it is nominal behaviour from PLC ?Yes, this is normal behaviour, which is described in the PLCnext Info Center:

Is there a way to prevent this firmware version restore ?Yes, this is also described in the PLCnext Info Center: