How does the Placing of planks work.
Placing of planks is handled as a two step process. An action icon/button process is used to plant the plank similar to placing a mine. The plank is placed on the ground and then a script handles linking it to link-able entity/objects I've created.

If the player moves the unit, or they react to close enemy during the action icon/button process. It can interrupt the process causing the plank to not be tagged, therefor the script does not take over and link it.

If this happens, there is an audio prompt and you can simply pick up the plank and try again.

When placing planks. Setting your men to hold position minimises them reacting to enemy.