The TXC command is implemented by bypassing the Link Layer & controlling the radio directly. The PA/LNA controls are done by the Link Layer hardware. So, in this case, the PA/LNA controls are not active resulting in the power loss. The solution to this is to put the PA control lines in GPIO mode and enabling the PA lines through firmware when starting this command and putting back to DDFT/LL control while exiting this mode.
Thanks a lot. I did exactly as you suggested and got it working.