I've not had it in C#, but in VB6 I've had things like this that were caused by an unarmed or out of ammo AI ship, in a system that I had a presence in.
The AI would move to a point where it was able to detect my ship on its sensors, which caused the interrupt, but didn't give a message because my ship couldn't detect it back.
And once it saw my ship it would move away since it had no way to attack it. Then it would move back towards it again because its dumb. Rinse and repeat.
Tended to happen in systems I'd cleared of Precursors. Using SM mode to dump 10,000 tracking stations on a body is a way to check a system for it.