Multiple resources on a task increase the work?

[Pesque]

Hello!
quite simple question, but tricky to solve, at least for me.
Create a task with Work = 40 h (=1 week for a person full time).
If you assign one resource 100%, you get 5 days as duration. Fine.

Now try adding a second one, putting both people at 50%: it is one person equivalent, so noting should change.
WRONG!! The duration increase.

Not satisfy? Then try with three people: the first at 10% the second at 20% and the third at 70%.
The duration is now 4 times the right one.
Of course the task is Type = Fixed work, so it should never change...

What is happening? Please help me, I'm going crazy...
=:-|

 

[IRstuff]

It's an old bug. You need delete the resources, reset the work and duration and enter the resources all at once

TTFN

 

[Pesque]

ok, thanks! Now it works better but not yet perfect!
It worked fine with 2 people, but still it have some problems with 3 people... (+66% in duration; before it was +300%!).

Something more to improve it?

Thanks anyway!
M.