Hi,
Are these thumbs external and are you starting new viewer instances when clicking them?
Normally there should be no errors of course, when the viewer itself stops its own downloads - but when the viewer itself will be removed - then the browser cancels the downloads requests - the viewer then only gets error events and thoughts that the loading has failed, more informations are not available here.
But a way to suppress the error messages, would be setting
showerrors=false .
Best regards,
Klaus