You can try add this further in custom.css file and adjust margin value accordingly :
div.mod-languages ul{margin-top:10px;}
I am unable to see any such error in debugging tool. Ref: Screenshot Nevertheless, Such css additions in custom.css file shouldnt impact less file, in question, as both are completely different files nor such css code has been added which could impact accordion file
Also, Such error shouldnt impact the canvas menu as the less file as being shown in your screenshot being dynamic preprocessor style sheet language which is being compiled into CSS relates to styling of accordion module.
You can always let us know if you face any issues with accordion module type being used for module titled INFO by opening new discussion
Cheers