Create /storage/.config/firmware/mediatek/WIFI_MT7961_patch_mcu_1_2_hdr.bin and WIFI_RAM_CODE_MT7961_1.bin then reboot and the files will be overlaid on /usr/lib/firmware and used instead of the embedded files.
Please try the latest firmware files from: https://git.kernel.org/pub/scm/linux/…t/tree/mediatek
If those are not working, an issue needs to be reported to kernel maintainers. If they are we can bump the embedded firmware.