Apparently my build maps roughly onto a trackway in the nether. Every couple of days I find randomly placed portals in various parts of my build and its getting annoying. Is there anyway to prevent this from happening?

Are portals being generated on the normal map?

Yes, the portals are showing up in the vanilla overworld, non-teckit server.

Plugin must be failing to stop them for generating, I'll look into it.

Random thought until the pluging gets fixed: do you have your own portal? If you do then that ought to suppress others within a reasonable range.

Alternatively have you been destroying the unwanted portals overworld side? If you do this but leave the nether side open then any time someone uses the *still open* nether side then a new overworld portal will be created near the old one e.g. right in your build. This is the most likely reason for portal spam that's centered on you, and the plugin can't prevent it.

You'd need to go to the nether, find another portal to get home by, then close the unwanted one nether-side.

Maybe this is causing the problem of portal appearing randomly. I've found this portal at [Nether Spawn] when a present sent me to the nether. The portal part [purple] do not vanish and just like that it hang there and teleport player back to the normal world. I don't know if because it is [Nether Spawn] or this may apply to all the portals out there that have been half disabled too ?

I've found another portal which are half disabled that are not around spawn area. That means its not only [Nether Spawn] the bug is applying to all portal that are existed in the Nether.