Seems like the development of this mod has stopped, the lastest update was released last year, issues + PRs on GitHub are growing.

I hope this is not the case, but without a response from the developer we can't be sure.

Maybe the developer is working on a new secret vehicle mod?

I think so, he's still actively updating his other more popular mods. I suppose he lost intrest in the project, understandable, working on the same thing for more than a few months gets boring.