I've got my own problem to ask too. Some of my fighters are not engaging the enemy even when I switch from Regroup to Engage with Z. It's weird as half of my fighters do, the Intercepter wing, but my Support wing stays by my ship, despite their Engagement/Support range being the same. Is it because of their role? Even the AI/autopilot can't make them attack.
Edit: Answered my own question by changing their roles and tag in their wing_data.csv from Support to fighter, now they are attacking, problem solved.