Problem with Xiaomi MiR3G

I have, until now, always used the snapshots version with my Xiaomi MiRG3G router.
But since the version after March 21, 2020, I can't update it anymore.
Either the router doesn't boot anymore, or it is very unstable and loses all settings after rebooting, and even Lucy disappears.
I tried again the version of April 24, 2020 as well.
After several resets I managed to make the wifi work for a while, then crash, reboot and nothing more.
I reinstalled the version of March 21.
What happens with the new versions ?
Is there something to do again to be able to install the new versions ?
I use the version openwrt-ramips-mt7621-xiaomi_mir3g-squashfs-sysupgrade.bin

Thank you for your answers.

Translated with (free version)

No one knows why I can't update?