Ubiquiti Nanostation 5AC Loco "Invalid version"

Hi there,
I just bought a nanostation 5ACL because I wanted to upgrade/replace my current AP.

Unfortunately, I am not able to flash openwrt, it always complains "invalid version".

I am running WA v8.7.4, the device was shipped with 8.7.9, but I cannot downgrade any lower than 8.7.4.

If I run hexdump -Cv /bin/ubntbox | grep '14 40 fe 27' it finds one line at 00009eb0

So I copy the openwrt via scp and run

hexdump -Cv /bin/ubntbox | sed 's/14 40 fe 27/00 00 00 00/g' | hexdump -R > /tmp/fwupdate.real
chmod +x /tmp/fwupdate.real

hexdump -Cv /tmp/fwupdate.real | grep '00009eb0'
00009eb0  26 a6 fe f8 00 00 00 00  af a2 02 fc 82 02 00 03  |&...............|

/tmp/fwupdate.real -m /tmp/openwrt-22.03.5-ath79-generic-ubnt_nanostation-ac-loco-squashfs-factory.bin

but that fails with Invalid version 'WA.ar934x.v8.5.3-42.OpenWrt-r20134-5f15225c1e'

Any idea how to solve this?

The last one of these I bought I had the same problem and ended up installing with serial.

The patch for ubntbox replaces the signature failure with a nop. So it is possible that the patched one now allows installing the unsigned Openwrt "factory" file directly without reverting the version. Or the wrong compare and jump has been patched out and now the binary is broken another way.

please tell me how to flash with serial