I have my Instinct Solar since 3 months and there were 3 or 4 situations where the clock was wrong. Every time wrong for -1 hour, so it was like showing 14:27 instead of 15:27. After going into the settings menu it switched to the correct time. But i don't know why, i didn't use anything special nor i had an activity before. Last time today, normal work day and in the afternoon -1 hour wrong.
Also i had once a weird display glitch. It was something like 22:30 and the first 4-5 pixels of the first "2" weren't displayed. Here the same "solution", going into the settings menu updated the clock and made everything ok.
I use the screen saver watchface without seconds.