I use waveshare 5.5 amoled screen, if I use display_rotate command, the video is very slow and lag, sometimes cause the audio problem. I have to use
Waveshare AMOLED on Pi5 and Pi4 with GPU acceleration - Volumio Development - Volumio Community
to accelerate the GPU speed.
Maybe the display is the cause ? so I suggest you try 1920x1080P HDMI TV to see if any difference.