Tablesorter Grouping not recognizing checked checkboxes

I have tablesorter runing properly on some table - it works fine. But first column contains checkboxes and I need to sort that column by checked ones. I have add grouping widget and it works fine on every single column except this first one - all rows are sorted under "unchecked" , just like widget does not recognize if it is checked or not. No error is thrown, nothing fancy in other scripts, just one checkbox in head column selecting them all (tried to remove it - no difference). Every script that I have reads checked/unchecked properly - just that widget is not.

Has anyone faced such issue? Can't google out similar situation.

Script is way to big to paste it here, so here is list what I use:

• tablesorter newest version, jquery 3.6.0
• widgets: group, zebra, filter, cssstickyheaders, dragtable

All config is cropped version of example in grouping widget page.(I don't have date /time columns)