4.5.2 animation BUG: 2D collider colliding with 2d trigger!!!

I've been developing my game for months now and only after i updated to the new unity version do i have this bug.

Basically I'm shooting a 2d bullet sprite with a 2D collider on it into a 2d collider sprite zombie.

The bullet collides as its supposed to and a sprite animation plays within which i set the zombie sprite collider isTrigger to TRUE.

BUT HERES THE BUG!!! If i shoot another 2d collider bullet sprite into the zombie sprite which is now a trigger collider, A COLLISION STILL OCCURS!!! AND KEEPS OCCURRING NO MATTER HOW MANY TIMES I SHOOT AT THE TRIGGER!

I've spent hours trying to figure WHY THIS IS HAPPENING and my only conclusion is that it's a BUG. This did not happen in any previous version...

I did a bunch of testing and narrowed it down to the animation window, when my zombie sprite dies it plays an animation which changes the collider to TRIGGER at a certain keyframe.

I placed a debug log function returning trigger status in the zombie script and it showed that the collider was TRIGGER(and the inspector as well), the bullet STILL COLLIDED WITH THE ZOMBIE SPRITE!!!

I even tried creating a new animation clip that only changed the collider to trigger and nothing else, so when i first shot the zombie it was set to trigger, but the second shot STILL HIT IT!!!

I'm going crazy over here, i just dont see how this is anything other than a bug...

and to add fuel to the BUG fire, i tried changing the collider to trigger by CODE and it WORKED! then i tried the animation method again and once more a collision occured...

Can anyone confirm? thanks.

UPDATE:

OK I loaded an older version of the game from 2 months ago when I knew 100% the bug didnt occur, and LO AND BEHOLD THE COLLISION STILL HAPPENS!

I'm now a 100% certain that this is a bug in the new version related to setting the rigidbody trigger in the animation window.

I don't want to send my whole project as a bug report, is there an easier way to let Unity know?

Can this possibly have to do with the extra settings in the physics2D options? maybe im not understanding something.