"A battle error has occured! Check the console for details and report this bug to the Pixelmon Developers."
The Delibird still lives after the battle. Battling him again drops nothing, but the second time the Delibird dies. I tried it in another new created server and same result. Same in my friend's PC. Tried also to change the time of my PC to a different December day (26th) and same error.
I also caught a Delibird after killing it first time but nothing special with it.
Since it happened not only in a deifferent server but also in my friend's PC, I think it is a mod bug. Can someone confirm if they have this bug also?