Clock is off by more than a minute. All Units You don't have a lock yet or if you do the time zone setting is incorrect. Make sure you have a lock and if the problem persists check the time zone setting. Unit turns itself off for no apparent reason on my motorcycle, offroad vehicle or bicycle Units with more than 2 batteries. This is caused by battery vibration.
Some batteries are shorter and narrower than others.
You can try a different brand of batteries. You can tape two together or place some tape around the batteries that will be on the outside to minimize vibration. You can gently pull the springs in the battery housing to make the connect tighter. You can ask Garmin for some small springs that will set between the batteries to make contact better. You can use external power.