What could possibly affect the speeds of that particular SIM?

Devices
1

Hello dear experts.
I have a question, it is a SIM card issue:
We tested some 5G activated SIM card on a mobile and its bringing 300 above (5G speeds).
Same SIM tested in CPE (router) and it is showing every 5G radio parameter, but not bringing the 5G speeds (although other SIMs are working fine in the router).
What could possibly affect the speeds of that particular SIM on the router?
Is it QCI issues or other Core configuration issues?

2

Below 2 things you may check :

  1. UE category
  2. APN in both devices