Thank you for your patience all this while, We have concluded our investigation into the issue and below is our finding.
This issue is due to the use of a specific version of Extensis Universal Type client: version 6.1.6.
The issue is reproducible only with Id 2018 as Extensis UTC 6.1.6 is not compatible with Id 2019.
If you are using Extensis UTC 6.1.6 with InDesign 2018 please use any other version of Extensis UTC which is compatible with Id 2018 to avoid this issue.
Or you can upgrade to Id 2019 and used compatible version of Extensis UTC.
InDesign TeamAnonymous commented
Same problem here. When opening the file, it is modifying the links to the date and time you open the file. After updating and saving the files revert back to their original time stamp - therefore they are modified again. Very annoying. I have removed the complete CC and installed one by one - still no joy.