InCopy and InDesign CC no longer syncing reliably

We are a publications office using full Creative Cloud. Up until about six months ago, we had a seamless workflow, using Google Drive: 

1. In-house designers create magazine layouts in InDesign and set them up so the writers/editors can "check out" text boxes for editing/updating copy. The designers leave the file alone while editorial works on it.
2. Writers/editors open the layout files with InCopy and make edits to the text using the "checkout/check-in" and "save all content" features. Layout changes are given directly to the designer to make in the InDesign file. The editors save and close out of the InCopy file.
3. The designer opens the layout file in InDesign and updates all links. The updated file reflects all the content changes. And we go on from there.

Now we're encountering problems with the ID and IC files syncing. Sometimes all the content changes appear in the InDesign file seamlessly. But, more often, only some or none of the changes appear. We've also noticed that the designer might have to open and close the InDesign several times—each time receiving prompts to update links—before the InDesign file opens without a prompt to update links. Even after all that, not all of the editorial changes appear in the updated ID file.

Any ideas why this is happening and, more importantly, how to fix it? We rely on ID and IC to be seamless, and we miss the efficiency and accuracy we had up until about six months ago.