1.12.6 - Crash when ally uses planning mode

[toma]

We were playing 2v2 on Path of Daggers. Ally - side 3 - (1.12.2 version) was recruiting units in planning mode not on his turn. Finally my (side 2) turn came, I started recruiting units and after recruiting 4th one wesnoth crashed.

Console output:
20161019 01:48:28 error engine: Trying to add - Wose-4294967294 - 4294967294 (31,5) over - Elvish Scout-4294967294 - 4294967294 (29,5). The new unit will be assigned underlying_id=9 to prevent duplicate id conflicts.
20161019 01:48:28 warning unit: assigning new id to clone of generic unit Wose-4294967294
20161019 01:48:31 error engine: Trying to add - Wose-4294967293 - 4294967293 (32,4) over - Elvish Scout-4294967293 - 4294967293 (30,4). The new unit will be assigned underlying_id=10 to prevent duplicate id conflicts.
20161019 01:48:31 warning unit: assigning new id to clone of generic unit Wose-4294967293
20161019 01:48:35 error whiteboard: side_actions::execute_network_command(): received invalid pos!
20161019 01:48:57 error whiteboard: side_actions::execute_network_command(): received invalid action data!
20161019 01:48:57 warning whiteboard: Move defined with insufficient movement left.
20161019 01:49:10 warning whiteboard: Move defined with insufficient movement left.
20161019 01:49:11 warning whiteboard: Move defined with insufficient movement left.
Segmentation fault.

Afterwards we restarted and another guy was his ally. He crashed as well.

[Pentarctagon]

Planning Mode is known to be problematic. I am not sure how much progress, if any, has been made towards fixing the bugs, or what the current consensus is on removing it.