Update: After more testing.... I can confirm the command works properly and smoothly when traveling from and into any dimension.... The issue described in this report tends to happen due to some kind of lag 

When using the new "/execute in" command to teleport to the nether from the overworld using your current relative coordinates you are teleported to your exact coordinates when you were in the overworld.... You would be sent thousands of blocks away from where you should be in the nether

The same happens vice versa from nether to overworld

Teleporting from the end to the nether (and vice versa) scales down your coordinates correctly

Steps to reproduce:

1. Start in the overworld

2. Type the command: /execute in nether run tp @s ~~~

Expected results:

Your coordinates are divided by 8 relative to where you were standing in the overworld

Observed results:

You will be sent to the nether standing in the exact number where you were standing in the overworld

The same happens vice versa from nether to overworld