The forcefields protecting the Axalon need the shield circuitry to regulate the shield's power when absorbing attacks. If the circuitry fails, a single powerful strike can permanently blow out the shield generators.
There is a reset switch for the shield circuitry on the Axalon's exit ramp. It is not clear if this is because the circuitry is prone to frequent failures, or if there is some circumstance when shutting down the shield circuitry (but not the shields themselves) is desirable.
This problem no longer appears after the Sentinel System was activated, as it appears that it upgraded/replaced the original shield system.