The GlassWire team will probably have some questions for you.
I'm just intrigued why you say 100GB is impossible. Because it happened over too short a time period? Because you don't connect using WiFi so your mobile data plan would have run out long before 100GB was reached?
I use Spotify (on Windows and Android) and over the least year or so I have had a few situations where Spotify has used "extra" network bandwidth. Unfortunately, even with GlassWire for Android I can't see the breakdown of external versus local data usage or the hosts and protocols being used.
- It "loses" downloaded songs and I have to download them again. I have to keep resetting the playlist download setting to download them again.
- An issue where it kept downloading the same song over and over. If I hadn't noticed it creating traffic on the GlassWire graph then I would probably have never known about it. I resolved it by restarting my system. As it didn't recur I didn't report the problem to Spotify.
- Where it updated itself, as it does when I start the program, but it got into some sort of loop. Again, it was fixed by a restart and hasn't recurred.