I have searched the possible causes of the error I'm encountering, and there are a few factors that have been suggested:
1- Interference--> I used different frequencies and ensured they are not in use.
2- Multipath --> absorption boards were used to minimize the impact of multipath.
3- Some people suggested to change the FFT length and CRC length as a potential solution, however, modifying these papermeters did not resolve the issue.
When I used a channel model instead of USRPs, the error did not occur.
I am still uncertain about the exact cause of the error I am experiencing.