On October 22, 2019, Sprint and device manufacturer Inseego pushed out a firmware update for the Mifi 8000 mobile hotspot which fixed a severe firmware bug. The bug caused the device to go into a reboot loop, but only when connected to certain towers - on other towers the device functioned normally.
When the Mifi was connected to a tower that exposed this bug, the device would enter a constant boot loop and become completely unusable.
The first confirmed reports of the reboot issue were in September 2019.
Inseego and Sprint were able to fast-track a fix for this problem, a huge improvement over fixes to Verizon's 8800L, which took the better part of a year to address.