eth_subscribe calls increase over time

I have been using dshackle for some time now. Overall, it works very well, expected when used with Quicknode. Using the websocket mode to connect to a Quicknode upstream node, the number of eth_subscribe calls increases over time. I have isolated from everything else. It is just Dshackle, connecting to one quicknode endpoint and no clients. I see dshackle reconnecting frequently and I suspect the old connections stay open, leading to an increase of calls. As soon as I restart dshackle, the number of calls drops.

Any idea, what could be the issue? I don't mind fixing it if anyone could share some ideas of where to look for the problem.

thanks.