Are you by any chance using a dependent event you made yourself? I found that when I made the simple pbRegisterPartner event, I got an error, but the one with Essentials worked fine. Also, don't fight a single trainer if you are using a dependent event, you should talk to the dependent event and select yes when prompted to deregister. Make sure the dependent event follows the template of the Brawly one in Essentials. I'm not positive about your other error, since I couldn't replicate it. Did you modify anything in the editor about the player character? If you have the pbChangePlayer, then the player should be defined, unless you changed something in the editor that makes it incompatible. If all else fails, re-download essentials and drop what you have so far into it (it's easy, you can go to the Data folder and copy the Maps (numbered Map001, etc.), MapInfos, and Import any images you may be using).