Description:
A nested condition is a condition that applies on a path coming from another condition. So in the following scenario,

X1-/-X2-/-U3
 |        |--U4
 |---U2

you'll see this incorrect allocation:

Instance    X1    X2        After X1    After X2
1                  T        T        X2             U3
2                  F        F        U2            U2 (does not reach X2)
3                  T       T         X2             U3
4                  F       F         U2            U2 (does not reach X2)


Symptoms:
Paths on nested conditions are not taken or the wrong proportion goes there.

Cause:
The issue is that the simulation engine sets the parameters independently on process instance start. The first conditional parameter is set to True and the second to True in instance 1. Then in instance 2, the reverse occurs leading to the scenario above.

XPD-7108 has been raised to address this in a future release. There is a workaround which is to include additional paths. This could quickly get unwieldy in bigger projects.

X1-/-X2-/-U3
|----||---U4
|---U2
|---|
X1 path 1 25%
X1 path 2 25%
X1 path 3 25%
X1 path 4 25%

X2 path 1 50%
X2 path 2 50%

X1    X2    #    After X1    After X2   
1    T    1    X2        U3
2    F    2    X2        U4
3    T    3    U2        -
4    F    4    U2        -
1    T    5    X2        U3
2    F    6    X2        U4
3    T    7    U2        -
4    F    8    U2        -

TIBCO Business Studio simulation feature does not handle nested conditions correctly.