Town waypoint dissapeared

So i am playing in act4.

I traded with someone who was in act3.

Then.... after trade i cannot go back to act4. It teleports me to riverbank.

Why????? i am halway through act4 with MANY waypoints enabled in act4.

There is no waypoint in act3. And if i go through yellow portal it also tp me to riverbank.

I am so confused.

Do i have to after each trade go back to riverbank manually clearing it every single time...? because it seems so.