Are you mounting the Google drive on the desktop using Google Drive?
Something similar to this?
And this worked in 10.14 but broke in 10.15, right?
Pinweels show up when there is a system lock that is stuck. This could be memory access, network access or file system access. This should of course not happen. I’ve never been able to trigger this accidentally or on purpose, and a standard application like DataGraph is not supposed to have that power. It does look like the fault is on Apple or Google, but I might be able to work around it.
DataGraph files are really packages which allows incremental saves. This means however that there is a lot of folder/file access when a “file” is saved. Some sync utilities get confused with this.
We will try to replicate this on our end. Are you using the Mac App store version (that adds in Sandboxing as a variable)? If you are, does this happen when you try the beta version?