It is most definitely a bug. It takes 20 seconds real-time to kill you, regardless of game speed. That means it could take less than 10 in-game minutes to kill you at normal speed or 4-6 in-game hours to kill you if you're at maximum game speed.  Was planning on starting a new CDDA run with the new update, but guess not, because hypothermia is practically unavoidable in that gamemode.  Edit: Tbh, the entire cold system needs to be reworked at some point. Im Canadian enough to know how warm/cold you'd be, and in almost every situation when my character is cold, I'm starting at them, confused as to how they're cold while actively fighting, wearing three layers, gloves, a bandana and a toque in like -2 Celcius.  At those tempurtatures, I could spend hours shovelling in a t-shirt and pants and i'd probably be overheating the entire time. 

nano ProjectZomboid64.json  In /var/log I haven't found any log related to PZ nor by running journalctl for the respective user.  

Also is are there any reports in /var/log that might give some clues?

How much RAM are you allocating to the server?

I just said that we had more mods in .18 and it worked fine.  We are using the vanilla 70 limit in both cases.