Thank you for your report. I faced this problem as well when I was using Visustella, so my first guess would be to disable as many other "core" plugins as possible and try again. I made a compatibility patch with VS, but it could be that I need another one for Yanfly Plugins.
I will add a patch for Yanfly Plugins, in the meantime you can try to track down any other plugin that may cause problems so I can fix those, too.