Test mode error message but not on test mode

Hi there, I have an Asset Clean Up error message appearing on most pages and posts on a site – it doesn’t show to visitors, only to logged in admin but it’s bothering my client. Test mode is switched off, I can’t work out the reason for it especially as it seems to apply to the WP Admin bar. I can provide a screenshot if you need, or let me know if you would like me to arrange a login so you can check our settings. Thank you.

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