My Whirlpool WRF555SDFZ09 freezer not as cold as before, even after defrosting it

Hi everyone, I’m having an issue with my Whirlpool WRF555SDFZ09 freezer and wondering if anyone can help.

• The freezer still gets cold, but it’s not as cold as it used to be.
• It used to have frost buildup, but I defrosted it recently, totally remove the back panel in the freezer, so there’s no frost now.

Does anyone know what could be causing this? I’ve already checked the basics, like closing the door properly. Any advice or tips would be appreciated!

Thanks in advance! 🙏