1 Answer. The portal must be rectangular (e.g. 3x3, 4x2, 3x5, but no circles). It has a maximum internal size of 21x21. It must be at least 3 tall, and at least 2 wide (not including the frame, with the frame that ends up as 5x4). If you build multiple portals in front of each other and light them, only the rear most portal will be visible, butPortal A was constructed first. It works completely as expected. Entering it and exiting. Portal B, which is about 100 blocks away, does not work when exiting. Entering works just fine however trying to exit gets stuck on "Building Terrain". This doesn't seem to be an issue with my world, as creating a new world in creative with the same seed (And you forgot to post the number of the Overworld portal that Nether portal 3 takes you to.) 200 blocks away in the Overworld is the equivalent of only 25 blocks away in the Nether so the 49 block difference in the Y coordinate is very likely to make Nether portal 3 be farther from its optimal position than Nether portal 1 is.
RESPONSE: I am not riding or transporting any mobs i am alone, i am not in sneak mode. I downloaded a local copy of the realm and had the same issue. I can stand in the nether portal for an indefinite amount of time and no animation happens at all for transport. I had minecraft and realm closed overnight on my pc and just logged in to try again.
Panel Reset. Head to the Apex Panel and stop your server. Scroll down until you find the World field. In this field you are going to see two buttons. Change World and Reset Nether. Go ahead and click Reset Nether. Type reset and press Reset Nether. Start your server back up and your nether should now be reset!Z0D25.