This controls whether the card automatically switches its transmit clock back to a preferred reference once that reference recovers after having failed. This is the card-level analog of nodeSyncAutoRestore: disabling it during a flapping timing reference prevents the transmit clock from repeatedly re-synchronizing and re-slipping every time the flapping source briefly recovers, trading automatic optimal-source selection for stability during a known intermittent fault. For example, a tech disables cardTransmitClockSwitchOver while chasing an intermittent BITS clock fault so the card's transmit timing stays put on the stable secondary source instead of bouncing with every brief recovery of the flapping primary.