This all I can find now:

Hoover-1 Product Manuals

The Parts and Accessories link at the bottom still works and may be somewhat helpful for some.

Unfortunately the below link doesn't seem to work now (December 2023).

The online version of the manual explains the error codes:

https://hover-1.com/hover-1-pioneer-manu...

Error E1 - Motor failure, motor needs to be replaced.

Error 2E - Accelerator failure, accelerator needs to be replaced.

Errors 3E - Motor blocking fault, release the accelerator.

Error E4/MOS - Mainboard MOS failure, replace mainboard.

Error E6 - Controller/instrument communication failure, the controller needs replacing.

Error E7 - Battery over-voltage protection, battery needs replacement.

Error E8 - Controller error, controller needs to be replaced.

Error E9 - Brake failure, brake needs to be replaced.

Of course this doesn’t explain everything but at least it is a start.

They do have some troubleshooting and parts on their web site:

https://hover-1.com/partsandaccessories