Rclone + gdrive + 55tb library can't complete scan

[jpat0000]

There are a few options you want to disable in Plex for starters:

Settings > Server > Scheduled Tasks > Uncheck:
"Perform extensive media analysis during maintenance"
"Refresh metadata periodically"
"Upgrade media analysis during maintenance"
"Update all libraries during maintenance"
"Refresh local metadata every three days"
"Remove old cache files every week" <-- Maybe

This will help prevent a lot of needless file scanning/folder accessing, however, it will not stop the issue you have. See:

[Feature Request] rclone mount: Cache the entire drive structure at startup, and add new files by monitoring Google's ChangeLog

Google Drive quota reached seemingly linked to folder scanning

Every time I have reached a download quota, it has been pretty hard to say what the cause is because I had in fact been downloading a lot of content each time, but what I was also doing was scanning tons of folders with Sonarr, and refreshing my large Plex library as new content gets added, with an rclone mount. I have had a few days where I have downloaded as much or significantly more content than previous problematic days, and had no issue, the link that I see, is that on these occasions, I …

You can break up your library into many sections, example: Sunday - Saturday, Kids, etc, refresh each section as needed. Your movie section is probably causing the most requests to Google as typically there are many folders, and Plex has to check every folder. You could save a lot of time refreshing and perhaps eliminate your problem mostly by putting all of your Movies in a single directory without any subdirectories. Example:

Before:
gdrive:Movies/BlaBla.2016/BlaBla.2016.mkv
After:
gdrive:Movies/BlaBla.2016.mkv