Missing Face Crash

[micheus]

I created the missing face by using the hole command. Then filled it in again.

maybe the way you did that?!
To remove holes you select a surrounding faces and use the Hole command with RMB option (that means, you select the menu command by using the Right Mouse Button - you must see that in the information line)

I also don't understand what you mean by "If you need "single" face grouped you must to use extract or extrude without thickness." because there is no thickness option for extrude or extract.

That was just an impression I had seeing the first image. And Yeah, the Extract command doesn't allow you to set a thickness, but for extrude you do that moving the mouse - you can keep it unmoved and finish the command and that will give the extrusion a zero thickness. You also can invoke the Input dialog, so you can enter a precise value of zero for distance.

Can you explain how to do cleanup in body mode? I don't see how to do that.

Body mode, means you change the Selection mode to Body (the 4th icon on the toolbar) which you can activate using the shortcut [B].
Then you select the "problematic" object and in the context menu you select the Cleanup - [LMB] option uses to be enough.