Thanks for the replies and tips! It's good to know the PVA tip needs to be cleaned more often. I'll just make that a standard practice at least every two prints. Our prints are pretty large and tend to take 20+ hours. It normally goes wrong pretty early, but it would be frustrating to have it happen towards the end. I have noticed that I have to do the cold pull multiple times, even when the hot pull comes out clean.
I haven't noticed the PVA pop and crackle, but I will keep an ear out. Dry boxes aren't expensive, so we could feasibly get one and rotate rolls.
I've cleaned the feeder twice now, because I noticed that chunks were missing from the PVA and was worried it was gunking up the feeder. It was pretty messy in there both times and there was a nice pool of PVA dust just below the feed as well. I loosened it some more after yesterday's cleaning. It seems to still be feeding fine, but without so many chunks missing. There are still some, but they're considerably smaller than previously. I'm still not sure why that's happening. Another group member thought it was because the nozzel wasn't heating properly and therefore getting stuck. I could see if the PVA got stuck at the nozzel side that the feeder would spin on the same bit of PVA and might take some chunks out, but we can't really stop to clean mid-print (can we?).