the exceptions class "onlinejudge_exception" is incorrectly located (and named) and so is the "judge_base" class in your judgelib.php file.

also most of the functions in your judgelib.php are incorrectly named, and the judge/sandbox/lib.php also looks wrong too.

for more information see:
https://moodledev.io/general/development/policies/codingstyle/frankenstyle#class-names

Please note that compliance with the frankenstyle naming is a requirement for plugins db approval.