This is a 3 gang model that might be similar enough as a start. This last post describes changing 3 switches into two. That should be helpful to go from three to four.
This post by @veeceeoh might be of help in debugging the driver, and I'm sure you'll get great suggestions from him as well.
Here's information on porting a Smartthings DTH to a Hubitat Driver, as it is called.
