I am having the same issue with the flashing "d" on my LEV II. I can't see any evidence of shorts on my board. How do I reset the slack switch? The elevator is stuck 2" above level on the 2nd floor.
On the bottom of the cab, on the rail side, is a micro-switch. This switch must be manually reset by pushing the button on the backside of the switch.
You also need to understand why it tripped.
As always, make sure you are not putting yourself in a compromising situation. There should be an e-stop on the first floor in the hoist-way. Make sure you know where that is and it is pushed in (i.e. stopped) while you are under the cab. Make sure the first floor door is open. I always put some automotive jack-stands under the rail where the cab would come down just in case.
Here is a photo:
https://access2parts.com/lev-manual-reset-slack-switch/