Yes, I bet it is the newer firmware. Pretty much everyone suggests to downgrade to 1.0.16 or 1.0.18:
https://forum.openwrt.org/t/tuto-openwrt-unofficial-redmi-ax6/111340#downgrade-the-official-firmware-4
It should be quite easy and straightforward.
I am going to switch from the stock firmware to OpenWRT tonight or during the weekend, but I still have a few questions.