There was an update very recently that (at least on my side) made the model worse than in the prior (which ironically, made the model work the best at the time, about four days ago). As the dev said in the pinned post, the model is still being worked on, and we are in for a very bumpy ride until things stabilize, but there is at least work being done.
Now, regarding the personality changes, there is something you may want to keep in mind because this may remain true even after the model is perfected: The context of the input has prevalence over descriptions and the recommendation instructions, so it is very difficult to have a character remain happy and joyful if the context forces the model to opt for a more "logical" approach changing it's character ("logical" in what the LLM training dictates, which often is "moon logic", but with trial and error it is possible to deduce the word combinations that causes a switch in the wild).
Here is a lengthy guide on the topic. It covers most of the pitfalls you may find. The only thing I believe is no longer a problem (although I may be wrong), is that the "caveman speak" problem seems to be patched already, but again, it is still in the guide in case you run into it and how to restore it. Hope that helps!