Going through a portal from flatlands to biome bundle https://gist.github.com/frenzye/14b1eb376ef56807795c933881c875e6

Thanks for reporting this, did this happen once or does it keep happening even after server/client reboot?

Keeps happening https://gist.github.com/frenzye/5ccd1d3e9a41f6610a126385a4cffcf8 Going between a modified flatlands and a stock biome bundle. Have dimensions turned on for both and have specified different portal types

https://minecraft.curseforge.com/projects/netherportalfix was the culprit

I've seen this before with other mods. It appears that some mod is replacing or removing the default teleporter registered to the world. I thought it was AbyssalCraft but I don't see that in your mod list. Could you try removing/disabling any mods that affect dimensions/portals, see if that fixes it and if so try to narrow down the problem to as few mods as possible?

Cool, thanks for confirming!