Bug "unspecified HTTP 400 error occured" in JIRA iOS app on Workflow transition screen

[nihalahammed]

While using JIRA Work Management in iOS app, I am repeatedly getting error message
"unspecified HTTP 400 error occured" 

Platform: iOS app
Issue occurs during worflow transition.

1. In first finding this issue happens when workflow A->B has a transition screen configured.
2. In second finding this issue happened when I tried to create a sub task in a status. In this scenario I had configured the workflow to validate if the created sub task status = Done when it moves from A->B or the workflow restricts the transition to next status.