Zipper5 noticed it during the ARMA 3 Survive Livestream a few days ago, so the issue might be fixed in the next big patch.

Voted up on this. I made a similar report back in November, but still to no avail :( On the bright side, at least the Tempest truck is working good.
Oh, and as of version 1.24.125979, it looks like they disabled that seat from the truck, so that solves the problem for now.