quitting and restarting Capture One does not actually work

Hello thanks in advance for your help with this.

I am shooting with a canon 5d2 on a macbook pro running El Capitan (10.11.3) tethering to Capture One 9.2.1 with USB.

Here is the scenario:

Sometimes Capture One stops working properly (usually tether connection)

If i restart the program appears to restart however the problem persists.

As restarting C1 has not worked I then go to shut down my laptop and the OS starts to shutdown (other programs start to quit)

At this point I have a dialog box pop up in C1 saying "Do you want to terminate the running activity" (this box does not show up when I try to restart the software the first time). The running activity is not processing raw files etc.

Then I have to click "terminate and quit application" and the computer shuts down.

Obviously I would prefer not to shut down completely as it is more disruptive than just restarting the software

I'm guessing the "running activity" is a process active that c1 is using that is not restarting when I am quitting the program? If anyone knows what this process is I could use activity monitor to restart it? Or perhaps there is another solution.

Many thanks in advance!