I had just finished a battle with a wild Pokémon, and I was choosing new moves for my Ledyba. During the dialog, I was vulnerable to attacks, and was killed by a zombie (caused by [this bug][https://www.pixelmonmod.com/tracker.php?p=2&t=13932], incidentally). After that, I was unable to initiate battles with other wild pokémon. Saving and quitting did not change that; however, a full client restart was sufficient to workaround the issue.

Thanks for the report. However, I wasn't able to reproduce it. I got killed by a zombie while levelling and I could start new battles fine when I respawned. Sometimes it is the case though where the game thinks you're still in battle when you're not, which sounds like what happened here. Like you said, a restart can fix it, but something else that should work is using the /endbattle command.