I had issues with tuning my trunk eddy board and strange behavior was observed with the trunk spinning too much or reversing motor direction. I got tired of tuning the board before playing each time so I bought the pinbit board. Yes it is a little more than replacing the original but -- for me -- it fixed my trunk issues and was worth it.
The other thing I did before replacing the board was disassemble the plastic housing (below playfield) where the optos are located (lots of plastic dust, good grief!). Gave it a good cleaning and checked the alignment. It helped a little, but the board seems to have been my real issue.