Returning from the nether, the game is not checking for existing overworld portals, and instead creates a new one about 80% of the time.

I found this too and it can be very annoying

Its happens to me when I link my portal to the right coords but I won't go to the nether 

My portals have since stabilized, but I'm stuck with two overworld portals to the single one in the nether. Will destroy one later to see what happens. Have so far had 7 separate overworld portals generate due to the bug.

• I also experienced this issue

• After some troubleshooting I found I had to make the portal within the nether and I had to try a few time to get it to link to the overworld portal

• Elevation seemed to be the factor that changed the outcome

This is very likely a duplicate of MCPE-39609 and is working as intended. There is a brief explanation on that ticket for how portal linking works.

However, if you provide the exact coordinates of the portals at the moment the player enters/exits along with where you expect to go this can be checked to see if it is in fact a bug.

Initial Overworld portal at 254, 10, 167

Portal in Nether at 30, 10, 36

Multiple portals appeared through the course of exiting the nether, ranging within 10 blocks of each other (X=250-260) (Z=280-290) at Y-64, and Y-30

Final Portal exit to Overworld 251, 64, 290

No new portals have formed through continuous travel, however, return to the overworld is through the initial portal about 5% of the time.

If it were working as intended, I shouldn't have that 5% chance to appear at the Y=10 Overworld portal.

Attached is a picture of 4 of the portals generated by the game. 3 more spawned around Y-30, which I already removed. The sole player built portal is at Y-10, about 130 (Z) blocks away.

I have never encountered this issue in any previous version of the game.

When you leave the nether through your portal at 30 10 36, the corresponding overworld coordinates are 240 10 288. More importantly, the search range for that is X: 112-383 and Z: 160-431. Your original portal is barely inside the search range and so if your actual departure coordinates from the Nether are only slightly different it will be outside the range.

I'm assume you broke each of the generated portals in the overworld before another was created close by.

Your best approach would be to move the portal on the Nether side to the precise corresponding coordinates to your original overworld portal, which would be at 31 10 20 in the Nether.

Based on the coordinates provided, this is working as described in the MCPE-39609 ticket and so this will be resolved as a duplicate.