Cannot save multiple files in Editor (Studio 2017 CU18)

Hello all,

Few days ago, I updated my Studio 2017 installation to CU18. 

When trying to open multiple files where one or more documents have comments, we get the "all-time-classic" 'object reference not set to an instance of an object' error message!

More about this error can be found here: /cfs-file/__key/communityserver-discussions-components-files/90/sdlerror_2D00_20191220_2D00_16h44m6s.sdlerror.xml.zip

In an effort to understand why this is happening, I revert back my Studio 2017 to CU17, and no error comes up when saving the same files in Editor. I've tried in Studio 2019 SR2 CU5 w/ no issues as well.

Kindly note that the comments should be translated hence the project settings below.

Any idea?