Whenever the DIM1 file is removed from the world folder so chunks can regenerate, the end portal and end gateways will no longer generate.

Deleting just the DIM1 file is not enough to properly and safely reset the end.
This issue describes a safe way to reset the end: AllTheMods/ATM-6#437

Hello, I looked at the link and desided to try something out of random, and by shear luck, It was a fix wtihout having todo anything super complex

all you have todo is simple

using a NBT data view like NBTexplorer open the worlds affected level.data and go into the forge entries and then open one called enddragonfight or something close to that

then look for these values

im not exacaly sure what one done it but by setting these 3 values to zero the game understood (but the mod mostly) recognized an issue and treats the end dim as the first time being loaded in, this in turn caused the frame that does not regenerate during a dim 1 delete. this in fact caused the frame to regenerate