Documenting a "funny" behavior of XPA3.X, which is also a difference in behavior from uniPaaS.
In a GUI form, add a Tab control and connect it to a numeric variable A.
Set its ItemsList property by giving both a static value '1,2,3', plus an expression that evaluates in runtime to '0,1,2,3' (the expression normally should override the static setting)
Now do the trick: In task prefix update the variable A with 0.
Guess what: in XPA3 the variable after updating will not have 0 but 1 (i.e the first acceptable value in the static list)
UniPaaS in this case, updates the variable correctly with 0 (since the ItemsList expression overrides the static value).
XPA keeps on ...surprising me with it's endless minor bugs and issues.