Dimension portal problem

First, I don't really know if there is someone with the same bug that I have but oh well.

The problem is that, in my mod, I made a nether like dimension with a custom biome, everything seems to work BUT when you enter the dimension, even if it's creative, you are randomly teleported in the dimension, in mid-air, in blocks, etc... even better, the portal doesn't create itself like it normaly would but insted it create itself in a random location(near to you) but doesn't tp you from where you came, for that you need to remake a portal where you spawn in the dimension.

Hope I have been clear and if not, I can send you my mod to test the bug.

Hope I can be help soon ! ^^