I have a clock w a radio receiver that used to work flawlessly and always kept perfect time. Now it can days to resync. What possibly could have changed?
I'm by no means an expert, but it could be interference caused by other electronic devices, the direction of the ferrite rod antenna inside the clock (it cannot get signal if it's pointing in the direction of the transmitter), or maybe the battery running low in the clock could also cause something like this (based on that the Pico wasn't able to power the receiver module in my experiments).