The issue with counting ligatures, is that it was very easy to correct a manuscript from masculine to feminine merely by adding a diaeresis. This scribal edit would be impossible to identify.

The examples below were written by Seth Knorr, and are being used to represent examples from manuscripts.

προστάτης (masculine)
προστάτης (masculine)
προστάτης (masculine)
προστάτης (masculine)
προστάτης (masculine)
προστάτης (masculine)
Correction from προστάτης (masculine) to προστάτις (feminine)
Correction from προστάτης (masculine) to προστάτις (feminine)