I am using register 0 to record my key sequences (i.e. q0 …. q).

In the recorded key sequences, I am yanking some text. After the first replay of the recorded key sequence, I am no longer able to play it back. Register 0 contains the text from the last yank operation. In your recorded key sequence, when the yank is performed, register 0 is overwritten with the yanked text. So your recording stored in register 0 is lost. You have to use some other register.