Cannot save as target "Failed to save target content: Sequence contains no elements"

Hello,

My coworker experience this error once she tried to generate a target .xls file. She was using the newest version of Studio 2017. The error occurred using both "save target as..." and "generate target translation.We ran verification but no problems were found. Also ran verification on the excel file in Excel and nothing seemed problematic. This error happened while I was away from the office so I couldn't help her so she was forced to painstakingly copy the segments individually into a file to create a target file. She needed the file right away.

The only "solution" that I offered her eventually was to recreate the project over again and repopulate the file using the completed TM data. It worked. But neither of us knew why it worked because to the best of her knowledge the project settings were the same and the file was the same. So why did it work the second time, we wondered. What does "Sequence contains no elements" mean? According to the knowledge base when we clicked the error window for "Failed to save target content..." it seems a redo is the only solution. I also just tried recreating this problem on my own computer and could not. Trados worked as it should.

Is it a safe conclusion to just immediately redo the project if such an error were to occur again? Or does anyone know any way to tackle this problem without a redo? Redoing the project was actually time-consuming (5-10 minutes or so) because many segments were split and combined so didn't get CMs or 100% hits after running pre-translate. Or is there a way to know that the file is corrupted from the beginning? I could tell my coworkers to run such-and-such a task first to make sure the translation can be generated. 

Thank you.