Good news, disabling plugins worked. I have several computers, so I think I may have narrowed it down to either spell-checker or inkdrop-vim. When I disable these two plugins, it does not yet fix the issue. I than close Inkdrop, and I receive this error each workstation I apply this solution, but the error only happens once after closing the app:
Reopen Inkdrop and viola pasting from HTML as Markdown works again. I than reenable these two plugins and pasting as Markdown continues to work even when I close the app and reopen.
Possibly this was the result of residual code. I’m not sure, but at least I am able to fix the issue on all my workstations.
Thank you for your advice!
– Dale