Aether portal blocks appear to use a float somewhere in their particle generation, which results in them being generated incorrectly when at great distances from the origin. Mojang paid a lot of attention to fixing these in 1.15/1.16, so fixing it here as well may be advisable.

Examples shown with a nether portal block for comparison, which produces particles correctly.

At 0,0: expected behaviour

At 20000000,20000000 (beyond 2^24): nether portals still work normally, but aether portals now appear to only generate particles on one side:

Precision loss confirmed: using FarLandsMod, at a billion blocks out, it seems to only lose precision in the direction the portal itself faces, where the other directions are completely fine.