In 1.14.3 I was able to prevent this bug by leaving the nether in the direction I was facing when arriving in the nether.
My overworld and nether portal are facing east/west and when entering the nether portal form the east side I come out at the original portal, when entering from the west side a new portal gets created.
My seed is -9060493524218898299 and the world is running on a server and was created before 1.14. The region my original portal is standing in is a 1.14 region because I build the portal in a 1.14 village. The nether region was most likely generated before 1.14.
OW: 581 52 3798/37999
N: 56 98 487/488
When leaving the nether by entering the portal from the west side a new portal gets created somewhere around 438 70 391