Minecraft; 1.12.2
SpongeAPI 7.1.0-SNAPSHOT-43d8496
SpongeForge 1.12.2-2690-7.1.0-BETA-3115
Minecraft Forge: 14.23.3.2679

Using the Sevtech Ages Modpack Current Version

Apon entering the beneath a portal is not made and the player suffocates in a wall.
Apon exiting the beneath using a portal you are returned to the original portal and torches are placed around the original portal placed to enter the beneath.
along with entering/leaving the dimension the following appears in console
https://pastebin.com/2VMLeyzE

ive noticed that regardless of the dimension you enter, even logging in, That pastebin error occures.
So no errors are thrown yet it doesnt spawn a platform on the inside of the beneath

The behavior you're describing is the exact inverse of the teleportation logic. Can you reproduce this without Sponge?
Also, that error is thrown from Journeymap.

Did you by chance enter the Beneath from any dimension other than the Overworld?

Same issue here, using sponge won't spawn the return block. Should we post in sponge?

Sorry I missed your second msg. No I tried it from the overworld

Once it's approved, 1.4.2 could potentially fix this, no promises though. If the small change I made there has no effect, then it's something that has to be patched on Sponge's end.

Closing this for now. If it's still happening, you might wanna report it to Sponge.