Table.sort only works sometimes (invalid sorting function for sorting)

[SyntaxWizard]

Fixed. The logic is still not clear to me but I found an answer after so many keywords:

Table sorting giving mixed outputs

If you pass a function into table.sort then the result of that comparator has to be consistent for each table element. i.e. if a < b evaluates to true then a >= b MUST evaluate to false, otherwise you will get the “invalid order function for sorting” error. This consistency can never be guaranteed if you use a comparator that returns true or false randomly.

This thread contains a lua-interpreted shuffler algorithm.