On Whitechapel when moving close to the ramp my merc would start repairing it; without me pressing F.
I was using Nader here.
(might not be map/merc dependent, but only had it happen to me once, yet)
(video has no sound)
[video=youtube_share;ECZ13MHDHtE]http://youtu.be/ECZ13MHDHtE[/video]