Thanks to EVSupport for the suggestion to check the 12V battery. I haven't had any problems with any of the 12V accessories including the winch, but out of curiosity I unplugged the UTV and turned off the main pack batteries (they have an on/off button, the US version doesn't have the "big red button" disconnect.) By the end of the day the 12V battery was reading 6V. The moment I turned the main pack back on I could tell it was charging the 12V battery, so the fact that I leave the UTV plugged in was masking the declining state of the 12V battery.
Briefly looked for a lithium replacement because of the longer lifespan, but couldn't find one that I was sure would work with the charging designed for the lead AGM battery. So just replacing with the same.