Specifically the "getExperienceGroup" error would be the "Ticking Memory Error" that has been showing up. The line it refers to "java:83 in the stats.Level class is the assignment for the experience group, and is getting NULL values in return, which based on the SQL interaction code indicates either invalid or missing records.
I have no idea how to find out if this is true, I know some database programming, but someone who is more used to the Pixelmon database might be better suited to check.
BETTER DETAILS AND TEMPORARY FIX FOR THIS:
viewtopic.php?f=10&t=4301