If the plugin isn’t listed there then it isn’t being loaded any longer. That is actually most likely where the problem is coming from. There are likely things in the project that the plugin either edited or supported and now since the plugin is gone, those items are causing problems.
I went to download the plugin to test it myself but it isn’t available to me as a purchase is required and it is not part of our marketplace. It may be best to attempt to contact the creator of this plugin as he/she may of had reports of this problem before.