Brings me to… according to my understanding of:
at least this smaller “issue”, at least one of five values you provided, is gone away. As @q4o449 kindly informed us about the method he/she used, as clearly described (sounds as quite reliable to me) within above related post, as related to 85°C value (I guess). If same described method works for you as well, you might post here new screenshot, reproduced one within same environment, same as described within your initial post (so we can move on).
I working in L5 without rebooting and drain battery to 59%. After that I run monitor and see again 85C in bq25890-charger. I poweroff L5, cooling L5 some hour, power on and bq25890-charger still show 85C.
I charge L5 without poweroff and rebooting to 75% and bq25890-charger work again (with and without USB charging).
Seems there is a battery charge border (between 59%-75%) below which begins bq25890-charger return invalid data.
So lets testing: During self discharge beginning at 70% bq25890-charger several times showed 85C and back to normal. Duration of Interval with 85C is random from 5 seconds to 20 second. At this time (65%) enabling WiFi causes 85С and disabling WIFI leads to normal after few seconds. At 62% I catch very long interval of 85C to 60% battery.
Self discharging of L5 very fast about 1% by 1.5-2 min at screen of Termal graph. I have no SIM and HWoff cellular (HW switches: off/on/on) and SWoff bluetooth, auto-brightness: off. Enabling/disabling WiFi has no visual affects to speed of discharging but case 85C bug earlier. Phone always warm and I dont see any correlation of 85C bug with real temperature of L5.
Ah, that may be because bq25895’s ADC readings are specified to not work below the VSYS_MIN voltage (which we set quite high by default - 3.7V). I’ll check whether that includes the temperature, but from what I remember I’d say it’s likely that the answer is “yes”. If that’s really the case, then well - just ignore these readings 
Maybe borrow a Non-Contact Infrared Forehead Thermometer from the nearest place where COVID regs require them to use one and get “ground truth” values. 
I had the same problem with the LED blinking 5x-off-5x, phone getting hot, battery discharging at a rapid rate and bq25890-chager temp showing 85.00°C in the Usage app. The phone’s kernal is on 5.16.11 and the battery life was around 4h.
I followed the instructions about charging problems, not thinking that it was very relevant, but now the bq25890-chager temp is at 40.00°C, the phone’s not as hot but battery drainage is quite significant. While typing this answer the battery is down 10%, from 82 to 72. Don’t know if this is a hardware fault or what to think of it.
Up to here linked page recommendations it is written: “Birch 8. When the red light turns off the battery is fully charged.” Please poweroff your Librem 5 Evergreen while on and (still) connected to its original power supply and wait until constant red LED light turns completely off. This should help to reestablish 100% of your Librem 5 battery capacity (up to 4.20V recommended max.). Charging rate should be around 5V/1.5A, even 5V/1.6A if your battery still healthy and not taking too long (such powered-off device charging will take several hours but might help with this quick discharging/drainage you described in your post, I hope so).
I needed to edit this post as same procedure already recommended in this thread: