PM sent. But...
I don't expect the image to help. If the device is booting enough for you to know WiFi is failing, and for it to connect to a PC, then it is unlikely to be an image issue.
The WiFi issues will almost definitely be related to Kobo withdrawing most of the support for the device. That happened when they had to remove older security protocols from their servers because those protocols are no longer considered to be secure. The older firmware on the Mini does not support the newer protocols. Kobo did a firmware release for the Mini to allow WiFi to continue working, but, they do not support syncing books.
The Kobo desktop should still support the Mini. When the announcement was made, this was stated as the way to do the setup for the Mini in the future. If you care getting WiFi connection errors using that, it is unlikely to have anything to do with the device. Make sure it is up to date and can sync your books.
You can also sideload the firmware. The last official release for the Mini is 3.19.5761-s. You can download it from
https://wiki.mobileread.com/wiki/Kobo_Firmware_Releases. And while they aren't officially supported, all later versions have been tested by people here and reported to work.
Of course, some of the issues could be because the SD card is failing. If so, replace it and use the image. You can use a larger card, but, I don't remember if anyone has tested a 32GB card in the Mini. Up to 16GB will work.