Sometimes a team will face a situation where the engine is looking for a run or pass play specifically, so the engine is only going to pick a play that is set towards that play call. For instance, if the engine is looking for a running play and you have 2 plays set to "Heavy Pass" and 1 set to "Favor Run", the engine will select the one set to "Favor Run" as the play. If there is a case where all of the plays are set to "Favor Pass" or "Heavy Pass" then the engine will use a default play which may be a formation that is not set in your playbook.
The most common instance of this is when a team is ahead towards the end of the game and the engine flags the team to start running out the clock. It will then start choosing more run oriented plays. If the playbook contains only passing plays, it will use a RB2-WR1-TE2 formation and favor the run.
If you want to have a pass heavy playbook, but want to limit the plays called in these situations, place one play in your playbook for each down and distance that favors the run and is set to "n/a" for the Normal Playbook and set to a formation for the Two-Minute Playbook. This way it will not be called during normal play of the game, but will be available to be chosen when the engine is looking for a running play.