I am running OnlyOffice 220.127.116.110. I notice if I have a document open for a while, make a modification, my changes are not auto-saved. Even clicking on the Save button does not do anything. I know that these features do work, but after some time, it seems there is some kind of connection disconnect or timeout.
As far as I understand, you are using Workspace. Please point me to the guide which you used for installation and let us know component versions (Document server version, Control Panel, etc.)
As for the issue in general, please reproduce the situation and provide us with videofile. Also please run a test: open any file > edit the file > close it and wait for 10-20 seconds > try to download local copy of the file and check if changes persist there.