61%  into downloading and I see this message and downloading ceased :(

I've googled for an answer but noting applies to my current version 1.99

I've followed what advice I could find that seemed applicable, file location, etc.

No option to force check.

Your HD may be dying. Use hwinfo to check its health reports, and back up your data and replace the storage device as soon as possible if that's the case.

You might wanna update your client.
I am not an dev, neither from the team, but reporting bugs of old versions, and not knowing previously if they where fixed already, is likely bad, at the minimum.

One of the suggestions is to delete some files that seems to be the bug, they are the files to be downloaded or have only one piece already, but are causing check fail; hash check bug.

You probably have something modifying the file while it's being downloaded, more info would be useful, like file extension and which programs you have running while it's dling.