Context was set to anywhere between 8k and 16k. It was responding in English properly, and then about halfway to 3/4s of the way through a response, it would start outputting tokens in either a foreign language (Russian/Chinese in the case of Qwen 2.5) or things that don't make sense (random code snippets, improperly formatted text). Sometimes the text was repeating as well. But I thought that might have been a template problem, because it seemed to be answering the question twice.
Otherwise, all settings are the defaults.
OpenWebUI connected tabbyUI's OpenAI endpoint. I will try reducing temperature and seeing if that makes it more accurate.