The bug

/teleport <targets> <destination> should do the following:

• Move each of targets to match destination's coordinates.
• Send each of targets to the dimension in which destination resides.

Here's what it actually does:

•  Move each of targets to match destination's coordinates.
•  Send each of targets to the dimension of the current command's context.

How to reproduce

1. Spawn a marker entity in the spawn chunks: /summon armor_stand
2. Enter the nether
3. Run /tp @s @e[type=armor_stand,limit=1]
   →  You remain in the nether, but your coordinates change.
4. Run /execute in overworld run tp @s @e[type=armor_stand,limit=1]
   →  You are transferred to the overworld and end up near the armor stand. The first command should have done this as well.

Dimension context should be overridden in this case, always using the dimension of the destination entity. For the /teleport overload that uses coordinates, the dimension context should be used (this works now correctly).