New nether portal automatically generated in overworld

Going back to the Overworld from the Neither created a new portal in the Overworld, mid air, instead of using the existing one.

What I expected to happen was...:
Going back to the original portal

What actually happened was...:
A new portal got created, which I got teleported to.

Steps to Reproduce:

(Save file: https://1fichier.com/?j37nniephoyvkcqkzhfm)
1. Go to the Nether

2. Go back to the overworld

3. Destroy the portal you arrived to by mining an obsidian block

4. Go back to the Nether with the original portal

5. Go back to the Otherworld

6. A new portal got created

Additional notes:

• The portal originally worked as intended (for the ~3 first travels)

• The bug appeared after altering blocks around the Nether portal in the Nether world

• The original Nether portal in the Overworld is below see level, adjacent in one of its side to sea water

• Original portal coordinates (XYZ): ~ -145/55/300

I am available for any extra information you may need