Probably need to see some logs to know whats happening. When you start the bot, you can open up the Quest Plugin tab and see what QP is trying to do.
I believe QP is just telling OldGrindBot where to grind (depending on your quest progression), and after the quest is completed QP changes OldGrindBot to the next area. Im sure its more complicated under the hood, but thats how i understand it to work (havent looked into the code, but makes sense).
Do realize Quest Plugin currently only does the main quest line, and none of the side quests. I believe at one point darkbluefirefly was going to add in the side quests to the public version, but he may have decided to keep those "dev only". Its his plugin and ultimately his call to make if he releases the side quests. Not a huge deal for your average botter. There are only 2-3 side quests per zone worth doing and you can just set OldGrindBot to those areas and it will complete the quests for you. Remember OldGrindBot does do all the quests as far as i know, and Quest Plugin just tells OldGrindBot where to go instead of you manually setting each zone.
When you are using Quest Plugin, make sure that you go into OldGrindBot and uncheck "Enabled Early Exploration Complete". If this option is enabled, OldGrindBot may reset the zone before you complete the quest, thus getting you stuck in an infinite loop and simply grinding the same area over and over.