Theme Setting crashed and won’t let me make any changes

Hello I am experiencing some problems working with a Vantage child theme – as soon as I touch ‘Theme Setting’ in the Appearance on dashboard something wrong happens. For instance when I try editing the thread ‘call me! maybe?’ from the gap and saving it, it loads a new page but still ‘call me! maybe?’ in the gap. At the same time the layout bound is locked into the ‘boxed’ without selecting the option and it won’t let me make any further change, any setting you can supposedly alter with ‘Theme Setting’ after this. Could I know if there is any solution, or do I simply need to use other theme instead?