That's odd! To confirm, does it show 'subscribed' on the channel page? Also, disable any third party extensions if you've installed on your browser: https://goo.gl/rNZvZx . Let us know if that clears up things for you.
Appreciate your efforts. Please send a feedback report directly from YouTube: https://goo.gl/WdI0BK . While every individual report may not get a direct response, we do review everything and use the details to investigate and fix issues.