Request: In handlers/views_handler_filter.inc, please increase the sort order weight option (#delta) of the exposed group filters to a workable number.
'#delta' => 10 to
'#delta' => 60
Reason: Sort breaks, and does unpredictable sorting, if you use more than 20 options. E.g. say you have have an exposed grouped filter with a price drop down of more than 20 options, sorting will not work after 20 items, it will always spit out a different order than what you specify.
You can see what's going on by showing the row weights, by clicking the "Show row weights" link:
What views does, when you drag and drop sort, is assign a unique weight to each selection up to 20, then after that it doesn't know what to do, hence you get unpredictable results.
Here's the fix:
If you increase the count of weight selection (#delta) to a sufficient number then views is able to assign a unique weight to each row...
Starting line 1000 change:
'weight' => array( '#type' => 'weight', '#delta' => 10, '#default_value' => $default_weight++, '#attributes' => array('class' => array('weight')), ),
'weight' => array( '#type' => 'weight', '#delta' => 60, '#default_value' => $default_weight++, '#attributes' => array('class' => array('weight')), ),