Hey there. Just to confirm, do you use any 3rd-party browser extensions? If so, it’s likely caused by an extension: https://goo.gl/YhjYEu . Also, does it shows 'subscribed' in the channel page? Let us know!
Please send a feedback report directly from YouTube with these steps: https://goo.gl/WdI0BK . While every individual report may not get a direct response back, we do review everything and use the details to investigate and fix issues. Thanks!