Sounds like Chrome is disregarding operating system level setting.
As a workaround, you can create (or find) an extension that simply calls preventDefault() when the contextmenu event fires.
For a long term solution, y
ou can search
crbug.com for an existing issue and star it. If you cannot find one, file a new issue using the "New issue" link on the same page.
Please, do not add a "+1" or "Me too" or "Confirmed" (or similar) comment. It just wastes the time of Chrome engineers and sends unnecessary e-mails to all of the people who starred the issue.
You can reply with a link to the found or created issue and might get triaged (and fixed) faster.