It's Happening Again...with Added Problems

Long story short, I am having audio issues with the wheel sounds again. Whenever a train passes by the camera, all I hear is popping noises instead of the normal track/wheel sounds. I had this issue when I first downloaded SP3, but the probelm seemed to have fixed itself after a couple runs. However, after installing SP4, the 'popping' problem persists. I've reinstalled the game (no effect) and re-downloaded every wheel sound I have (also no effect). I know I posted about this issue before, but I cannot find my previous thread in the forums (either through my profile or via search). So asking again, has anybody experienced this issue since installing SP4, and if so, did you find a fix?

Second problem: is it standard that you have to manually add drivers to your trains now? Before, most (if not all) trains were already populated with drivers, but now whenever I run a session, I have to go through and add drivers to every train that I want running (either by myself or by AI).

Thanks in advance!

You need to tick the box that says populate all empty trains in, edit session, driver setup.