Its on a public server, so I think that it is the latest version.

The issue is that Xerneas's z-geomancy boosts a bit too much, so its stats become higher than they should be. I used pokemon showdown as a comparison, but pixelmon boosts it a bit too much. normally, z-geomancy boosts +1 attack +1 defense +3 spatk +3 spdef +3 speed. In pixelmon, z-geomancy boosts +2 attack +2 defense +4 spatk +4 spdef +4 speed. It may be intended, but I am not 100% sure.

Thanks for the report, I was able to confirm this. According to Bulabpedia, "If powered up by a Fairium Z into Z-Geomancy, the user's Attack, Defense, Special Attack, Special Defense, and Speed are raised by one stage each (before Geomancy's charging turn)." This does occur, but then occurs again on the second turn (when Geomancy is activated and should normall just give +2 to Spa, SpD and Speed), thus giving too much of a boost.

Hello there! We're currently clearing through older tickets, and upon testing this issue, it seems that Z-Geomancy still increases stats twice, when it should only increase stats once on the first turn. As such, I'll go ahead and move this issue to internal to be fixed. Thank you for your report!