Bug report.
It's been many cycles since I did the Telos quest in my current run, but I just recently noticed something pretty strange going on with an independent station (in this case the Kassadar one from Tahlan's Shipworks; as such, I'm not sure whether there might be some mod compatibility thing going on, or if it could have happened with any other vanilla independent station: my guts tell me the latter, as that colony isn't particularly special except for it having a custom submarket for modded ships, but it's just a feeling).
The station seems to eternally be engaged in battle against an invisible fleet: at least on the sector view, as when you look at your military options in the colony menu, you can see the fleet is tagged as Luddic Church and definitely looks like your Telos flashback mission one, with that unique capital and the horde of Hegemony ships.
If you get there with the transponder off the menu allows you to "aid the attacking forces" (which should also trigger if you are hostile to the independents), but when you go into the actual battle there's no other ships, only yours. If you are instead recognized, you can only participate in the battle as a defender if you are hostile to the Luddic Church (as per usual): however, even if you destroy the fleet - which in this case does indeed spawn in the battlefield - the station will remain in that "engaged in battle" mode as before, only against an empty "unknown attack fleet".
I even tried destroying the orbital station with a kill console command and wait for it to regenerate after the repairs, but as soon as it respawned the engaged in battle situation kicked back in.
Only other experiment I did was trying to invade the colony (with Nex) to see if the issue would persist after the faction change: and unfortunately the permanent battle engagement does come back as soon as the station is repaired even after the takeover. Only, this time you can't even see any "military option" in the colony menu, nor you can interact with the supposedly ongoing battle in any way. However, at that point you can remove the orbital station alltogether from the colony management menu, and when you build a new one from scratch, finally the problem seems not to come back.
Now, as aforementioned, my game has been going perfectly fine for many cycles since I first noticed the issue and even much before that since when it triggered (I'd think during the Telos quest, for obvious reasons, although I have no proof of that), so nothing too bad is probably going on and the bug is relatively harmless. Even if it doesn't cause leaks, crashes or similar severe issues though, a station permanently in such an engaged mode might mess with certain things such as raids, Nex invasions logic et cetera: it being tied to an independent colony - at least in my case - definitely lowers the chances of such events overlapping (IE: no faction tries to invade independent planets in Nex), but I can't be sure the same would apply under different conditions.
I
guess Kassadar could have been the colony where I got the Telos mission (it's a size 5+ independent market as required by the mission to trigger, and one I visit very often as I play with Nia's ships a lot), but it was relatively early game, it's been a couple weeks, so I definitely can't confirm that as I don't remember, don't even have a save from back then anymore. I would imagine perhaps you had to anchor the flashback mission fleet to something for it to work, and the code fails at removing it afterwards? Just speculation, of course, you obviously know much better what might be going on under the hood.