Unusual for external regulators these days, lucky to see it.
The regulator on the outside is what should control any voltage spikes, although if the rectifier is dying, it might allow a reverse voltage, which electronic stuff won't like. If you can isolate the rectifier, a simple resistance test should show high in one direction for each diode and low in the other. Although if they only occasionally fail, the voltage from a test meter is unlikely to show a fault. If the diode pack is available and easily replaceable, it would be worth doing.
Can you connect a voltmeter temporarily to watch while driving to show if any spikes occur?