Hi!

With clock symptoms showing up, the first thing I'd look for is a battery or
large capacitor on the board...either one could be responsible for keeping
the clock running. Personally, I'd bet the thing has a battery like a CR2032
in place to keep the clock running.

Many designs will only use the battery when it's needed, but some pull from
it all the time. If the unit were to be stored in the absence of wall power,
or if it uses the battery all/most of the time even when plugged in, the
battery should last 2-3 years.

William