As the input voltage rises when power is first turned on, the output follows the input, allowing the regulator to start up into very heavy loads. The input-to-output voltage differential is small during start up when the input voltage is rising, allowing the regulator to supply large output currents. With a high input voltage, a problem occurs where removing an output short does not allow the output voltage to recover. Other regulators also exhibit this phenomenon, so the behavior is not unique to the UA78M.

The problem occurs with a heavy output load when the input voltage is high and the output voltage is low. Common situations occur immediately when removing a short circuit after the input voltage is already turned on. The load line for such a load has the possibility to intersect the output current curve at two points. If this condition happens, there are two stable output operating points for the regulator. With this double intersection, the input power supply is potentially cycled down to zero and brought up again to make the output recover to the desired voltage operating point.