Really strange "overlaps or collides" problem

Hi,
i'm having a strange problem.
I have an actor "A" that has a timer that spawns actors "B" on random positions on the screen.
Actor "B" has a rule: When overlaps or collides with actor "B", destroy.
This actually worked for 2 weeks OK, and just started... well, not working.
I tried with When overlaps or collides with (any other actor), destroy; and this worked.
Also tried putting a tag on actor "B" and making the rule When overlaps or collides with Actor with tag; didn't work. Worked OK when colliding with any other tags
I really have no idea why this doesn't work. As I said, it worked OK, until an hour ago.
Please help, because I'm stuck
i'm having a strange problem.
I have an actor "A" that has a timer that spawns actors "B" on random positions on the screen.
Actor "B" has a rule: When overlaps or collides with actor "B", destroy.
This actually worked for 2 weeks OK, and just started... well, not working.
I tried with When overlaps or collides with (any other actor), destroy; and this worked.
Also tried putting a tag on actor "B" and making the rule When overlaps or collides with Actor with tag; didn't work. Worked OK when colliding with any other tags

I really have no idea why this doesn't work. As I said, it worked OK, until an hour ago.
Please help, because I'm stuck

Comments
Other actors were movable, so overlapping with them was OK.
And I just remembered there was a post like mine a week or two ago
So a reminder to everyone: Overlaps or collides Rule won't work if both actors are unmovable!