Mob exiting a minecart via an activator rail will be teleported back to the first nether portal in the overworld it went through after entering a nether portal in the nether

Step to reproduce :
1. Have a nether portal in the overworld linked to one in the nether.
2. Build a second nether portal (5x5 this time) in the nether above the one already there (mine was built at y 118) (so it links to the one in the overworld)
3. Build some rails with the activator rail in the middle of the portal (1 block in front of it, not right next to the portal).
4. Build a cage so the mob does not escape and can only go to the nether portal.
5. Place a mob (Elder Guardian for my case) in a minecart and make it go on the activator rail (where the nether portal is). It may make it teleport back to the overworld nether portal OR make it go through normally (it’s not consistent)

Expected result :
The mob gets transported to the overworld.

Actual result :
1. The mob gets transported to the overworld.
2. The mob teleport back to the first nether portal in the overworld after entering the nether portal in the nether instead of going to the correct nether portal in the overworld.