FW probably is HMD-2.1.4 2019-09-10.150132.
For Google Store install additional software package for OFW v2.1.7 with paperclip will work on that FW too.
Force factory reset with paperclip without have connected a USB stick or from Setting/Advance/Backup & reset/Factory data reset/Reset device.
If display is 4K use TV mode remote button to switch video output resolution maybe will get stable image.
Try control box with Hicontrol from a other Android table/phone.
LE: HMD-2.1.4 2019-09-11.161658 include Google store and technically same with HMD-2.1.4 2019-09-10.150132.
Probably you have a reason why not want try upgrade to OFW v2.1.7 or other version.