When in creative mode and you enter a nether portal with an elytra, you arrive with the same coordinates as you were previously.
Example:
1. Entering a nether portal in the over world at X 500 and Z 500 and then appear in the nether at X 500 and Y 500.
2. Entering a nether portal in the nether at  X 500 and Z 500 and then appear in the over world at X 500 and Y 500.

When arriving to the other dimension the nether portal is invisible but it exists as you can still go back to the Overworld or nether when you walk through. a new portal is created at X 4000 and Y 4000 and walking back through this portal would create the portal that was invisible.

This bug was resolved in a prior update but it has came back.