The phrase "questionable quality" refers to something that is uncertain or doubtful in terms of its level of excellence or value. It suggests that there are doubts or concerns about its overall worth or standard. Full definition
The sound quality coming through isn't terrible, but reports of questionable quality during phone calls was a bit of a disappointment. (androidcentral.com)
If you are playing on search engines with questionable quality, even a few days away from your reports could cost you thousands of dollars. (searchmarketingstandard.com)
When it comes to friendship, we have more «connections» but are they of more questionable quality? (blog.politics.ox.ac.uk)