It's doesn't happen every time, but it happens more than 50%:
1. In mission editor, load attached repro mission "17931_endless_healing.Stratis.zip".
2. Note player is group leader, is injured and has two AI under his command, one of whom is a medic who is far away from the player.
3. Preview mission.
4. Go prone.
5. Order the medic (unit 3) to heal the player.
6. Before the medic arrives at the player, order unit 2 to heal the player.
7. As unit 2 tries to heal the player, turn so they are directly in front of you.
8. Observer unit 2 provide first aid to the play multiple times, and gets stuck to player.