@Ahmed, thanks for your interest to my issue.
"Have you tried checking the sim card on another device and if you are able to change the PIN on other device without any issues ?"
Yes, I reset PIN lock and change PIN in anaother device.
"Did you tried both the sim slots if both acts same?"
Yes if I remember correctly I got issue on SIM1 and SIM2.
"Also did you tried some other different sim cards , may be different ISP if it works ?"
I get same issue with 2 different SIM cards, first time replacing Orange France SIM card by Free France one, and a second time by replacing SFR France SIM card by Orange France one.
"Could you retry after re-flashing the firmware in boot loader mode?"
I would like to avoid any risk of a significant router outage. Also router location is quite difficult to access and to reproduce issue I would need to access it physicaly in order to change SIM card in slots.
For my information what is the purpose to flash the same FW from boot loader mode ?
FYI, not sure if there is any relationship with the issue, but when I switch from one SIM slot to the other one, I apply a specific profile for which the SIM I target is the default SIM (I used then 2 profiles where the only difference is default SIM slot). I used this way for switching SIM cards for a long time without any issue with 2 SIM cards not sharing same PIN. I got issue only when I replaced a SIM card with another one with a different PIN, but I think it is worth to know how I swicth from one SIM slot to the other, as this is when I performed this switch operation I got PIN issue (SIM doesn't connect and then I was able to observe in another device the PIN is locked due to some erronous PIN entries, while in the corresponding SIM profile the PIN code is correctly filled)