Low RPM mode in reverse

[spinspoker]

I have twin DF90’s from 2004 and on my port engine when in reverse goes into a very low rpm spin (almost like a trolling mode) and beeps at me from the throttle.

This only happens in reverse.

Thank you for your thoughts!

[boats.net]

Not sure why it would only be in reverse but start with neutral switch on engine is working properly and adjusted correctly.