Hi Abdullah,
I’d consider the idea brought by esakkimuthu and I recommend you to check it out first. However, in my opinion, the error should appear if the layout bitrate and the bitrate set at your transmitter are varying. For the solution, the easiest way from the schematic prospective would be an attempt to change the modulation scheme from internal to external. It’s known that external modulation is more stable then internal.
Let me know if one of these first simplest steps would work and we’ll go from there!