Where do you stop when failing to move past an opponent?

Question

There's a narrow corridor with me and other two creatures in it, an ally and an enemy:

WWWWWW
----M--AE----
WWWWWW

M stands for "me", A for "ally", E for "enemy" and W for "wall".

With my last possible action this turn, I want to move past E, in order to flank them, using acrobatics - A lets me pass but I fail the acrobatics check, and my move suddenly ends.

According to this question, I can't end my turn in the same square as A.

Where am I at the end of the move action?

What if there are other empty squares near to both A and E, like if E is in the first square of a corridor?

Answer 1

There are two critical excerpts from the CRB on this topic:

Squeezing: (...) A creature can squeeze past a creature while moving but it can’t end its movement in an occupied square. (...)

and

Accidentally Ending Movement in an Illegal Space: Sometimes a character ends its movement while moving through a space where it’s not allowed to stop. When that happens, put your miniature in the last legal position you occupied, or the closest legal position, if there’s a legal position that’s closer.

When you fail your acrobatics check, your move ends. Since you're currently sharing "A"s square mid-movement, that is an illegal space to end your movement (per the first quote). The second quote directs you to move to the last legal position you occupied, or the closest legal position if there's one closer.

This means you would end up:

WWWWWWW
------MAE------
WWWWWWW

In the event that you have two allies in the way and a wider corridor with a choke point:

WWWWWWW
--------NW-----
---M--AAE-----
WWWWWWW

Starting your movement from position M would leave you at position N after a failed tumble through E.