It's a fairly large hex correct? I would try to find a torx that needs to be pounded in (since likely no room to swing, prob need to use a lever to press it to in.

Work it around in circles (eg push at 12,3.6.9.12 o'clock). This method often works. You are basically broaching a star shaped hole.

Ideally you would cut a concave dent at the end of the torx to help pull the chips into the center.

Best if you can start with one size and bump up to another. Eg T43 then T45.

For a normal hex bolt I do the same idea but I use spline hex sockets.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)