https://clips.twitch.tv/InspiringRamshackleLousePRChase shows a nether portal I built yesterday after having been loaded in after a PC restart.

steps to reproduce:
build nether portal around 55ish kilometers out from where you spawn in
turn off PC
turn on PC
log in
observe changed nether portal?

Expected behavior:
For nether portal blocks to not be at a right or an oblique angle to the nether portal frame