The container block issue is probably more of a WordPress problem – just in the same way it’s hard to select a group. You can simply click into one of the container elements, and press the up arrow to get to the container. I don’t see this as an issue with the plugin itself.
As for it working sometimes or not – sounds curious. Unless your page isn’t loading properly it should either work or not work, rather than being intermittent. What versions of WordPress and plugin are you using? What is the problem specifically?
Lastly – how is it a “poorly written plugin”? Perhaps you can contribute some better code?