Could not find parallel task TaskId ... in list ...

Summary

Using @: fails with runtime error message Could not find parallel task TaskId ... in list ...

Steps to reproduce

Minimal example:

module TOPL2
import iTasks

Start :: *World -> *World
Start world = doTasks assign_error world

t :: Task Int
t = enterInformation []

assign_error :: Task Int
assign_error = toUserConstraint "bob" @: (t >>? return) >>- \v = viewInformation [] v <<@ Title "Bob entered:"

What is the current bug behavior?

Immediately when program is executed, the browser window displays the exception error message: Could not find parallel task TaskId 5 0 in list TaskId 4 1

What is the expected correct behavior?

Correct behaviour is that after launching this program, and starting another instance and logging in as bob, the distributed task task t >>? return should be available for execution to bob and terminate as soon as bob has entered the continue button. The original task program should display the value entered by bob.