sounds a bit like my recent experiences: Occasional Crashes with Raspi 3B+, Allo Boss Setup
I think I found an answer to my question on how to preserve logs after a crash (although in my case I cannot distinguish between a crash and a lost wifi connection, as I realize now, since I’m running the pi headless)
In short: I’m copying the log contents on file change to the volumio home directory, which is permanent: Not good for the SD card, I guess, but good for post mortem analysis. The weird thing is: Since I set the log copying up, volumio never hung up like before. I still see the temporary lost wifi connections in the log every once in a while, but for a week now they reliably recover and I can log in via ssh over wifi.
I suspected a bad wlan connection, but the raspi reports a signal strength between -48 and -52 dbm, which I think should be sufficient. I’ll keep monitoring…