I do not know if this is generally valid but I've found a solution for this error. If you call a wait for a job in a sub (Number2Sub) which is resumable sub and is called with a wait for then the ball is lost completely. So the answer is do not call wait for in a wait for.
B4X:
Sub Number1Sub
Wait For (Number2Sub) Complete (Result As boolean)
End Sub
Sub Number2Sub As ResumableSub
dim hj as HttpJob
hj.initialize("code1", Me)
hj.download("http://www.somesite.org")
wait for (hj) JobDone(job As HttpJob)
If job.success then
'Never fires
End If
Return True
End Sub