Double click on empty space. Option Show desktop.

Do you mean that you have to click 4 times for the Show desktop action to activate?

I'm not sure what can cause it, I haven't encountered this kind of an issue. Perhaps it a conflict with another customization tool.

In fact, it takes one click to set the focus on the taskbar and double click to minimize all windows. I tried to close processes in Task manager and the problem went away when closing Punto Switcher. 

Sounds like more of a Punto Switcher bug than a 7+ Taskbar Tweaker issue. The implementation of the tweaker for double click handling is very simple and standard. I'm marking it as not a bug, let me know if you find a reason to assume otherwise.

Thank you for your hint about another customization tool. I've already written to the technical support of the Punto Switcher program about issue and am waiting for a response.