eeschema undo: missing junctions when undoing delete.

Undo in eeschema (master branch) does not always work correctly.

To reproduce:
1) Select a block with some junctions.
2) Delete it (del key)
3) undo (ctrl-z).
   The un-done deleted part now does not have some of the junction symbols.

Attached there is a simple project to show the behaviour.

(See the attached images for the before-after the delete+undo operation).

Dragging the wires make the junctions on the dragged part re-appear, so it seems that the wire is connected but without the junction symbol.

I also had a (probably) related issue on undoing operations on much more complex schematics, where also bus segments appear like they were copied from somewhere else, but that is quite erratic and I did not find (yet) a way to reproduce that in a deterministic (and simple) way.

Note: Stable version 5.1.4 works correctly.

Cheers, Dino.

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Application: Eeschema
Version: (5.99.0-139-gbb596ebda-dirty), release build
Libraries:
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Platform: Linux 4.9.0-8-amd64 x86_64, 64 bit, Little endian, wxGTK
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