Lmsys hasn't released any official 4-bit version. It might be a better idea to wait for the official 4-bit version. But it is interesting to learn that the third-party 4bit version has performance degeneration.
I reject your premise that the 8 to 4 bit quantization is the cause of the vicuna fine-tuned llamas very average performance though. This hasn't been the case for any of the other 8 to 4 bit quantizations. It would be a unique outlier. And so I don't think this is the "cause" here.
which has been fixed recently.
Lmsys are launching new training jobs after this patch, please stay tuned.
edit: Oh, I was completely wrong. That's in the training not the inference so it applies to all the weights.