I suspect the error was caused by a corruption somewhere. I'd suggest deleting node_modules and reinstalling. Maybe even try clearing your npm cache.
If you've set a strict nbbpm-compatibility the plugin shouldn't get listed in versions not matched as far I know.
Additionally you could deprecate your npm package in order to make it clear that it's out of purpose these days.
This way you're doing the best you can (and should) to state it.
I don't know if the NBBPM checks deprecations thought.
But if it does since it's not a new publish you may have to manually PUT your plugin to trigger the update - I don't know whats included within the update-list the NBBPM checks regularly.
If it's not getting noticed by the NBBPM it probably should, ping the devs then.
reference where to find how to PUT the NBBPM: https://community.nodebb.org/topic/6267/outdated-packages-on-the-nodebb-package-manager
The nbbpm checks new packages that get added to npm, so if you unpublish your package, we won't know.
Best bet would be to keep the package there so users on old NodeBB versions can still install it, but put an
nbbpm.indexed = falsein
package.json, so when it comes through from npm, nbbpm will know to remove it from the index.