Just to confirm, does it show 'Subscribed' on the channel page. Also, do you have any 3rd party extensions installed? If yes, please remove the extensions and see if that makes a difference. Keep us posted.
Appreciate the info. 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, we do review everything and use the details to investigate and fix issues. Thanks.