I experienced this bug during my 10 day trial of Sailfish 4.5.0.25 on Xperia 10 III as daily driver for test purposes. I did use GPS and Android apps and then some time later there was no sound anymore, I use talefish as folder-based music player but the seconds were running very slowly, no sound from media, Webbrowser and no ringtones, just dead silence. Also in Portugal very close to Fuzeta that was pictured by kanguru007, but the SIM from a German provider. In Juni I will be in Germany and can test country-dependency, but I am skeptical about country specific effects, but who knows.
Very annoying behavior to have no acoustic notifications about incoming calls. Currently I can not provoke this no-sound behavior reliably, it is coming out of the blue more or less. No suspecious high RAM or CPU usage in SysMon during this no sound, no Bluetooth involved, only a reboot restores sound