Letters not printing well

Hi everyone, and thank you in advance for your help!

  • 3D Printer Model: Ender 3
  • Slicer: Cura (Tried different versions
  • Hardware Setup:
  • Problem description: As you can see in the below photo, the printer works more or less correctly, but I’m facing with an issue every time I print and I try to add letters. It always leaves some space without cover of the PLA filament.
  • What I tried: Changing temperature of the PLA / PLA material / Changing wall configuration, etc

Thanks again to who can give me some ideas on how to solve it!