Can't check out frame: You are currently editing 'filename' in another frame.

[#1]

Hi, 

I'm working on a prospectus with my team and using InCopy with them for the first time. One of the copy editors has encountered this issue where she can't check out a frame and message says You are currently editing 'filename' in another frame. Screenshot below of the message. 
The text frame is a threaded frame to another on the following page as its a continuous table but she gets the same message on the frame too. 
She's working form the ICMA assignment file I emailed to her. I'm aware this isn't the best workflow, the project team didn't want to use dropbox due to a whole host of IT issues we are having at the moment. She using InCopy Version 16.0.1.

Does anyone know whats going on because I can't work it out for the life of me? And she can't package the file for InDesign to send back to me until it's checked in. 

Thanks so much for any help in advance! 

[#2]

Sorry its an ICAP, not ICMA! 

[#3]

Not the best workflow is an understatement. You don't say what IT issues you're having but get them fixed and stop using that workflow. It's nothing but trouble.