That's strange! What device are you on? Does it show that you're subscribed from the channel page and Subscriptions Manager? Also, do you see this happening for other channels too? Let us know.
Thanks for confirming. Please send a feedback report directly from YouTube with these steps for us to work on it: 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.