Unit ghost exists for permanent as their unit type count (Can't say about money for that unit didn't paid attention, but I think that they "stuck" too) if you called unit in and lost control of any entry point few seconds later(before unit comes on battlefield).
Can't say if it happens every time, but I'll try to recreate this situation.

Thanks.

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Supposedly, losing sector control doesn't prevent the units already on the way from reaching the battlefield. Are you sure the "ghost" units do not go away a little later when the corresponding units appear from the sides?

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Nope. The ghost was standing till game end, even when I returned back entry sectors, it happened once, so I'll try to recreate situation today.

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Never apologize for being right!