Enemy crewmembers still being healed after using an Ion Bomb on their medbay

I just finished a round of FTL using the Gila Monster. My strategy was to put an Ion Bomb in my enemy's medbay and then teleport over my Mantis crewmembers. Normally this worked quite well, but on a few occasions something very peculiar would happen.

The Ion Bomb successfully detonated inside the enemy medbay. The medbay flashed blue, indicating that it was successfully ionized. I teleported over my Mantises into the medbay, where they quickly engaged enemy crewmembers. However, the enemy crew were being healed inside the ionized medbay.

Unfortunately I don't have a screenshot, but this is what I observed in game: the enemy crewmembers had the green healing animation playing around them and when I moused over them I confirmed that their health was in fact rising in between my Mantises' attacks.

I don't understand how this is possible, given that the maximum power that be channeled into a medbay is 3 and the ion bomb does 4 ion damage. This happened at least three times across various sectors.

Can anyone think of an explanation for this? Some augment maybe? I'll try the same strategy tomorrow and upload a screenshot if it happens again.