Basically as the title says, if I'm wearing my leggings of the burning mantle and they're activated, I can't activate my portal (well I can maybe 1 time in 20-30 if I am fast enough). The rest of the Kami armor has no effect. If I get too close to my portal while wearing the leggings I find I have to deactivate my armor / take off my leggings and wait around 5 minutes before it can be activated again. This was tested with portals in 3 different locations and was repeatable. The error is always "Error, Portal blocked!" I'm guessing that the cause of it is the light the armor produces which lingers in the area for a while. I imagine the portal detects this and assumes that the portal is blocked.
You are correct. The light that is spawned by the pants is actually a tile-entity. Tile-entities are things that do something more than just be a block. Like, a chest can be opened, or a torch that lights up an area. Now, your pants creates a new block. It is invisible, you can walk through it. You would not be able to detect it all, if it didn't emit any light. Now, the portal checks the area for any obstacles. If the invisible light is in the portal area, then that block =/= air, which the potal checks. I heavily advice you to find your keybinds to (de-)activate the automatic light from your Kami pants. Should be in controls
I added the tile entity to the whitelist, please try again to use the portal with the leggings and let me know if it works.