"Re-set Code" bug problem?

Is there a problem with the challenges on the front-end development,HTML and CSS?
I successfully completed some challenges e.g. import Google font and change font size.
If I press “Reset code” to try to do them again it seems to find a lot of errors in the same code.
Is there a bug problem and if so what can be done to fix this and re-try the challenges?
Thank you