OM 617 Motor Mount center bolt won't thread back into place

[lyricsboy]

I've been following rg2098's excellent motor mount replacement tutorial here, and I've managed to insert the new mounts and screw in the hex bolts that mount them to the frame.

Now I've got the engine lowered most of the way back down and am attempting to refit the center bolts that hold the engine to the mounts. The passenger side went in with no trouble, but the driver side bolt is not threading into the hole on the bracket attached to the engine.

When I was removing this bolt, I unscrewed it most of the way, but it wouldn't come out simply by unscrewing. I had to grab the head with some vise-grip pliers and pull it out. I didn't have to pull too hard, and it didn't sound like anything was breaking or stripping.

Anyone have any idea why the bolt wouldn't thread back into the bracket? I've looked at the bolt's threads, and they seem fine. The mount on this side was totally wasted, so I would imagine that bolt/bracket has been under some strain.

Thanks in advance!