Characters Jensor Sano and Freya Crescent on Adamantoise server. We ended phase 4 at level 18. We continued the main quest together during early access and went into Sastasha. When we should have reached level 19, it said we both reached level 20. Our experience bar on the UI still said level 18 but the character window said we were level 20. After we completed the instance and zoned out, the experience bar then said we were 20, matching our character window information. We have since progressed to level 21 with no other oddities.
http://i.imgur.com/tY9frRg.jpg