Why is my Realme 6 having weak network signal reception?

Hello, I am using a Realme 6 and recently I have been experiencing weak network reception. The phone often struggles to detect mobile signals properly, even in areas where other phones show strong coverage. Sometimes the signal drops completely or becomes unstable, making it difficult to make calls or use mobile data.

What could be the possible reasons for this issue? Is it related to the internal antenna, software, or SIM card slot? And how can I fix it?

Thank you in advance for your help.