I’m sorry you are experiencing these problems. A few other users have this problem as well, but unfortunately I was never able to reproduce it on my system, which makes it impossible to fix.
The rewrite of the Toolbox that I have planned will begin with a revamped chart export function, but it will take quite some time before I can release a beta version due to time constraints here at my end.
News! I’ve released the very first alpha version of the XL Toolbox NG (‘next generation’). It has almost no features so far, but a lot of work was done under the hood