Wrong sorting in widget pivot table

Hello,

I have pivot table as widget.
pivot table

The problem is, as you can see, when I sort by avg(Plnění normy %) there are few rows which should not be there on top. I made sure that Plnění normy is type Number and is not empty in any record. Interesting fact is that it keeps happening only for rows where avg(Plnění normy %) < 100. That would indicate that it is working with it as type Text. Why is it happening when Plnění normy is Number?

Could it be that when I firstly created the table (database), I set Plnění normy accidentally as Text and after some time I set it to Number?

Thank you.