How to further improve the transmission rate in ESB 2.4G proprietary protocols?

[Cytheria]

esb4mbps.zipI want to verify the 4Mbps transmission mode of the nRF54L15 series through ESB samples.But the highest value measured so far is 2.34Mbps, which is much lower than 4Mbps. Please tell me how to further improve this to validate the mode.