Spotify Android app CONSTANTLY logging me out and deleting all my sh**

[11102182237]

my setup
- i have this (https://bit.ly/2MfLe8S) in my car, you'd think spending 300 bucks would get you a decent car radio.... guess again

- android 9 

- 16gb internal

- spotify 8.5.18.932

- 32gb stick (https://www.saturn.de/de/product/_sandisk-sandisk-ultra%C2%AE-fit-usb-3-1-flash-laufwerk-2383249.htm...)  i bought 6 days ago (new) to save all spotify data

car radio tablet setup: stay active for 1 hour without ac power

my problem: spotify keeps logging me out. now, this isnt a new problem with spotify not liking external storage, so i did my research here in this forum and tried all of the below. 

now, since i'm on a very short fuse here is what i've been trying for the last 5 days:
-clear spotify cache

-clear spotify data

-reinstall spotify

-"log out everywhere"

-format usb stick to ext4 fat32 ntfs exfat

-factory reset

part success: exfat, (login survived 18 hours) --> tried to reproduce logout by ANY combination of cutting off power, wifi and standby state and spotify's "offline mode" -->no hickups after trying said combinations for 2 hours straight,  so i went to bed thinking problem is fixed with exfat. next day startup fine, couple of restarts fine, and then out of nowhere after shopping spotify be like: "login **bleep**"

now, before anybody suggests that its the usb port or the usb card: its not, google maps and every other single app installed with savedata on ext_ works perfectly fine. 

i thought i narrowed it down to being a problem with wakeup from standby state, but as mentioned above,  it aint. 

i realise that i appear to be an a-hole right about now, but please understand that i have been sitting in my car for a combined time of 20 hours over the last 5 days downloading my 17gb library dozens of times via 20mbit internet and am running out of options beside ripping out the radio, wrapping it up, sending it to elon musk so he can fly that s... to mars. 

since there is no hotline, nor support ticket system in place i beg the members of this forum to only read and only write solutions that actually have worked before.