The post-attach process in Companion 8.4 is particularly prone to misbehaviors, especially during login. These issues stem from the unpredictability of the order in which devices attach, particularly the battery and the controller itself. The following problems are well-described:

Battery suddenly appears to drain to 0% capacity (often reporting "battery level at 50%" first). This seems to be associated with cancelling a login after the controller has identified the battery; on the next login, it attempts to finish the handshaking process, only to discover that the battery's UUID has changed and is no longer valid. Ejecting and re-inserting the battery should update the relevant information and stop the controller from reporting that the battery is empty.

Teleport subsystem (FTL) disabled, especially repeatedly after teleport, and issue recurs even after applying a full power profile. The Core Services Bus module believes the controller is stuck in emergency power mode (5% power or less), and is restoring the emergency power template accordingly. This also seems to be caused by the controller erroneously reading the battery as empty. When a full (or nearly full) battery is properly recognized, this template isn't cleared because the power level is above 10%. Changes in Companion 8.5 should reduce the frequency with which this problem occurs, but in the mean time it can be resolved with a partial SSM reset, i.e. reset bonds followed by reset power.

Sudden spike in temperature reported by ATOS, resulting in loss of system integrity and being unable to boot, possibly occurring more than once. ATOS has incorrectly identified the charge level change caused by inserting the battery as incoming power (i.e., from a zap.) Several efforts have been made to quash this bug, but it still occurs from time to time. Repair the unit and then try reset sentinel immediately after booting up to prevent repeated overheating. Note that this can also be caused maliciously by a high-powered energy weapon, although a bug in 8.4.2 and 8.4.3 actually causes the system to ignore most such nuisances.

These bugs were not well-understood at the time of Companion 8.4.0's release, and due to their rare nature are most commonly encountered by controllers that have been in service for some time.