First of all, make sure the problem is not a compatibility issue or an error in a plugin that you’re using. To achieve this, we recommend you to deactivate ALL your current plugins except the one you use for your editors, and switch to a default WordPress theme like Twentyseventeen, then encourage your editors to make changes from different browsers.

If the problem is solved with this measurements, then definitely the issue resides in a plugin installed on your website, try to discover which one, and find another alternative to perform what that plugin does.

Please let me know if this approach solves your problem.