This sucks. When I create 2 linked portals in the nether and enter one side from the overworld and exit the other portal in the nether, the overworld turns into a red void and subsequently crashes the game.

Sometimes this happens instantly, other times it happens 10 seconds after.

I might add that these portals (in the nether) are 15 blocks apart, and are linked using their respective overworld coordinates.

Link to pastebin crashlog https://pastebin.com/z9aVeSHW

Please upload the world and give exact instructions on how to reliably reproduce this.

It seems to be tied to render distance. I found that if the render distance is anywhere between 2 and 7 chunks inclusive than its fine, but when it is 8 chunks and over the crashing starts to happen.

Having 3 portals in the world lowers the maximum render distance to 3 chunks. with 3 nether portals active the game crashes at a 4 chunk render distance. I assume a 4th portal will make travelling to the nether and back impossible without crashing, as the max render distance then would be 1 chunk, which is impossible to set.

Can confirm, when increasing my render distance to 8, it'll crash with your test world.

BetterPortals Crash.zip
Walk through the entrance of the first portal, then come out of the second portal.

I also found out that the game crashes when there is only one portal, but this world was the first time I tried building a 'gateway' in creative with the mod.

Tested on Recommended and Latest forge builds, using default Minecraft Launcher java properties. Also tested with higher RAM allocation (8gb from 2gb). Same story for all.