Error appearing when trying to reassign a task to a user who has rejected it

Hi, 

We are having some issues with rejecting and reassigning tasks where an error is appearing is certain scenarios. I have attached both the error and the assignment configuration from the node. The steps taken are:

1. User1 accepts and then rejects a task

2. User 2 tries reassigning to User1, the error appears. 

1. User1 accepts and then rejects a task

2. User2 returns to all assignees and the reassigns to User1 no error appears. 

It seems to be an issue with the rejection of a task. Is this a known functionality or is there a way for us to avoid having the error message appear as it is not a great UX?

Thanks, 

Niki