pin timeline to top when at top not working

I’m using Tweetbot on a 2015 Mac Mini running El Capitan. My favorite feature of Tweetbot is the pin timeline, but it doesn’t work anymore. The tweets accumulate and a black counter keeps track of how many tweets are not streaming. I have to use the spacebar to see new tweets. I’ve tried re-installing, deleting cache - nothing seems to work. Any ideas why this might be happening? Thank you. I’ve contacted support through your website as well.

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