N55 Valve cover bolt seized

[Ramps]

A month ago I replaced my leaking oil filter housing and oil cooler gaskets on my 2014 X5 35i xDrive and I was going to do the valve cover gasket while it was all apart but the bolt on the back corner, the one you can't see and can barely reach by the fire wall on the passenger side was seized. I could feel it twisting a bit but wouldn't break loose like the rest so I just tightened the rest back down and put it all together again.

Now I'm getting an occasional burning oil smell so I know it's leaking on the exhaust manifold.

Anyone ever had one of the bolts seize? It's the worst one to have this happen to, I think I'm going to just have to twist till it breaks and hope there's enough sticking out of the head to heat and grab with vise grips.

Side note, anyone try a non-OE valve cover? New OE is like $650 CAD and aftermarket are $250-300 CAD.

TIA

[turboawd]

Oh boy. That sucks. Only thing I could suggest is using cordless impact drill and socket on it, if you can reach with it. Maybe the hammer action will break it loose.