SharePoint Online - OneDrive - Read Only Sync Error

[Nicolle Brice]

Hi, about a month ago several thousand of our document libraries based on content types started syncing to OneDrive in Read Only mode. When viewing the library in OneDrive, green padlock symbols appear alongside files and folders. The cause – although the site content types show columns as optional, mandatory columns from the parent content type have re-appeared behind the scenes – hidden from view.  These columns were made optional or removed on the site content type, but for some reason they've re-appeared.  The parent content types don't even have mandatory columns anymore. 
To fix:

1. Go to “Library Settings” then “Advanced Settings”
2. In the first option, choose “No" for “Allow management of content types” and click OK
3. On this next screen, in the Column section you will see the culprit columns are marked as Required.
4. Click the columns which are required, and change to option “Require that this column contains information” to No
5. After changing the columns back to optional, the folder in OneDrive should become available immediately.
6. Then go back to “Advanced Settings" and enable content types again
7. Finally, check that the files are again editable in OneDrive.

This fix provided by Microsoft support is not acceptable due to the number of libraries affected.  Is anyone else experiencing this issue?

[#2]

@Nicolle Brice  Thank you for this. it helped me to resolve this issue for me.

for more information - 

https://support.office.com/en-us/article/invalid-file-names-and-file-types-in-onedrive-onedrive-for-...

[#3]

@Nicolle Brice 

We have the same experience. Required check out, approval and column are there for a reason. We have loads of workflows that use this

[#4]

@Shanaka Naranpanawe glad it helped.  

[#5]

Great post! Helps me a lot with multiple customers @Nicolle Brice 

[#6]

Same. Thank you for posting so that I could resolve my issue quickly.

[#7]

@Nicolle Brice 

I experienced the issue where all opened docs defaulted to read-only (and not Protected View - there was no option to edit) on Friday (Dec 13). The library I am in has no mandatory fields, but is synced with OneDrive for Business. I tried unsyncing the library to see if that fixes it, but am unclear if it is linked to mandatory metadata from a parent content type like Nicolle was talking about, or if it relates to something else.

we cannot afford to keep metadata optional or keep syncing and unsyncing folders - has anyone tested toggling the metadata between mandatory and optional as a fix? I am curious if there is lag between when the metadata is made mandatory and when the read-only issue occurs.