I have one but under ISO-TECH brand and IPS 2010 model but same thing.
Was dead and after repair was de-calibrated.
I abandoned at that moment because of other projects.
I remember I dumped firmware and saved somewhere.I found it some time ago and give it a try with my little skills in reversing firmware.
Ghidra got confused since for that mcu in 16 bit mode have missing some instruction that are available only on 20 or 32 bit, can't remember, I posted on github on issue, get some fixes but still no go since on 16 bit can't decompile, on 32 bit can decompile but wrong addresses.
Anyway I remember that was a check at startup for something on serial port that may trigger calibration mode and looks like interactive from strings on firmware.
Can't be sure but may be enter key pressed, need to search on work PC, if memory not fail me the check was for 0x0A that I think is Line Feed
I'll upload tomorrow firmware. Maybe someone with greater skill can do reverse engineering.
( if I don't forget)
edit
Just remembered that I uploaded on github
https://github.com/NationalSecurityAgency/ghidra/issues/5901#issuecomment-1777612940