sometimes permits are not going to be available. That's not a bug. That's things working as intended. If the system currently works by granting a particular faction the ability to give permits out for their home system then it's totally possible to drive that faction back to their home system.
Indeed, if it's intended to be locked off like that, it's not a bug. However, I'm unconvinced that these particular systems being locked out is intentional, and I'm hoping my bug report will address that one way or the other.
Fixing this "bug" would require changing how permits to faction home systems are implemented. You would have to create a new mechanic for acquiring permits that doesn't require physical access to the faction that controls the permit. You'd essentially have to move control over permits to systems from the factions that call that system home.
And this is exactly what Frontier did with the Tiliala permit in November last year. Black Fleet drove the permit giving faction into retreat so that it was only in Tiliala, in a roleplay fashion. Frontier then created a new megaship, where that faction lives, "In Exile", in order to make the permit accessible. (They also made it so that Black Fleet can give the permit too).
You can read about it from the official source here:
https://community.elitedangerous.com/en/galnet/uid/5a057eceda59a26bc40b9828
Probably a good idea ...but I wouldn't call this a bug and I wouldn't expect an acceptable solution any time soon other than hand-wavium adding the faction into an external system.
Tiliala. And adding the faction to an external system would be a perfectly acceptable solution.
If it's intentional, I'm fine with that, but Frontier have (I believe) confirmed that some permit locked areas are for future content (e.g. locked bodies in Sol, Lave, Diso, the large areas of space that are locked off, etc), but they haven't said anything about these 5: 4 Sextantis, CD-44 1695, HIP 54530, LFT 509 and Mingfu. I think it's actually quite reasonable to assume that the permit giving factions were simply driven back into their home systems and Frontier didn't notice, as permits that aren't directly story/content related probably don't get looked at that often by the development team.