Datatables sorting does not work at all and filtering acts weird

I got a datatable which is loaded properly on ready and displaying the expected amount of records coming from my database.

Table init is pretty basic:

$(document).ready(function(){
$('#nameOfDataTable').DataTable();
});

It's getting confusing if i do either try to sort by colum or filter.

Case 1: Sorting
Selecting a column for sorting results in the sort-symbol of the related column being activated/updated BUT the data is not sorted at all (same order as before).
No error output in the Javascript console.

Case 2: Filtering
If i do filter using the default search field it might either:
* Show 'No records found' in the first line BUT still display the other records below
OR
* Nothing happens at all

This depends on the search term but i can't really see a clear pattern in the behaviour.

Again - no error output in the javascript console.

I tested this in both Google Chrome and Mozilla Firefox.
Other data-tables in my project do work properly.

I am clueless what might cause this error in this particular table.