Thanks for reporting. This is indeed a bug. Same can happen with barrels/etc., while they are moving.

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I'm kinda meh on bug status for this. At least, I'm not inclined to try fixing it.
Was one of the very first things I tried when adding them.

This can also be done with graves, leading to resurrected hogs trapped in girders (commonly done in clean slate to slow a hog down a little). It can also be done with moving hogs, and, yes, barrels. Even crates if you get the timing juuust right.

To me it isn't terribly different from trapping something w/ land spray, so not too worried about it. I think adding checks for it to girder/rubber placement would be kind of annoying.

Maybe possibly could cause a small area of erasure around a trapped hog or airmine? Dunno. That seems kinda game breaking and anyway, could still trap by placing nearby, so don't see what the difference is.

Strategically seems a handy thing to have if you're willing to spend a girder to keep a mine from hunting you.