1.) You press the appliance too hard onto the skin.  Try to keep gentle skin contact.

2.) Check the appliance and the epilating head for broken parts. If the epilating head is damaged, replace it. If you hear loose parts rattle inside the appliance, stop using it and call the Philips Consumer Care Center in your country.

3.) Appliances with shaving head: Clean the shaving unit according to the instructions in the user manual. Especially check if any hairs or dirt got stuck below the foil and/or trimmer.
Lubricate the shaving foil with a drop of sewing machine oil.