I am a KS 10 fan and the only minor drawback for me is the two device connection at a time limit.
Out of curiosity, I listened to audio books from my library’s Libby App with my hearing aids as the Bluetooth audio device on my Windows 11 desktop, my Samsung phone and my Samsung tablet. My hearing aid settings are Automatic. The sound quality using each device was perfect. I have never tried audio books before…they would probably put me to sleep.
Because of my severe hearing loss, I have custom ear molds.
Anyway, I would guess leucurus’s problem is not his KS 10s. I would try streaming from a different device.