The strobe systems uses hellish amounts of juice.
I was taking a look at one and couldn't find a DC power supply beafy enough to power it. (over 15 amps).
Turn everything off and see what happens.
From the readings you mention 18amps dosn't seem to bad .
Check the voltage on the DC bus should be +14. if it is +14 the reg is fine.
Bat shouldn't be an issue during flight or with the engine running because all it does is except charge so if the DC bus is +14 everything is OK. It only comes into play when the alt voltage drops below 12V.
These electrical probs are a complete pain and most airframe and engine boys are in as much in the dark as the customer
MJ