Disabling memory Read Protection failed

Hello, we have boards with the MCU STM32F746. This works normally but in two cases we had a problem with the option bytes. Several values were changed and now we can't remove the protection.

The first board we tried several times to change level protection of 1 to 0, and finally we done it.

In the second board, at the moment it's not possible for us. The level is the 1 and we don't undestand why we can't go back to level 0.

This is the configuration of the options bytes

OPTION BYTES BANK: 0

  Read Out Protection:

    RDP         : 0xFF (Level 1, read protection of memories) 

  BOR Level:

    BOR_LEV     : 0x3 (BOR off, POR/PDR reset threshold level is applied) 

  User Configuration:

    IWDG_STOP   : 0x1 (IWDG counter active in stop mode) 

    IWDG_STDBY  : 0x1 (IWDG counter active in standby mode) 

    WWDG_SW     : 0x0 (Hardware window watchdog) 

    IWDG_SW     : 0x0 (Hardware independant watchdog) 

    nRST_STOP   : 0x1 (No reset generated) 

    nRST_STDBY  : 0x1 (No reset generated) 

  Boot address Option Bytes:

    BOOT_ADD0   : 0xEFBB (0x3BEEC000) 

    BOOT_ADD1   : 0xF5EF (0x3D7BC000) 

  Write Protection:

    nWRP0       : 0x1 (Write protection not active on this sector) 

    nWRP1       : 0x1 (Write protection not active on this sector) 

    nWRP2       : 0x1 (Write protection not active on this sector) 

    nWRP3       : 0x1 (Write protection not active on this sector) 

    nWRP4       : 0x1 (Write protection not active on this sector) 

    nWRP5       : 0x1 (Write protection not active on this sector) 

    nWRP6       : 0x1 (Write protection not active on this sector) 

    nWRP7       : 0x1 (Write protection not active on this sector) 

And when we try to remove the protection this happens:

SWD freq   : 4000 KHz                                                                                                                                          

Connect mode: Under Reset                                                                                                                                       

Reset mode : Hardware reset                                                                                                                                    

Device ID  : 0x449                                                                                                                                             

Device name : STM32F74x/STM32F75x                                                                                                                               

Flash size : 63,999 MBytes

Device type : MCU

Device CPU : Cortex-M7

Disabling memory Read Protection...

Error: Disabling memory Read Protection failed

Regarding the power supply, it's stable.

Anyone know who we can solve it?

Thanks & best regards