Dolphin Surf battery losing power while parked over night

We've only had our Dolphin Surf since October of this year, but for some reason it's happened a few times now that the car loses battery life over night, e.g. range of 140km when coming home yesterday, turned off and parked outside overnight and a range of less than 100km this morning. Is it normal for the battery to lose that much range overnight? It's cold outside, but not that cold (we're in Austria). This is our first EV, so we're a little bit confused, any insight would be appreciated, thanks! ETA: ok, I think the example mentioned above can be safely stored under "range estimation dropping due to temperature". Most of this is secondhand information from my mother, who primarily uses the car. Like I said, we're first time EV owners, so we're still a little green behind the ears. Another incident my mother wanted me to share on here after I told her about this post: the other day my mother left to do some errands with 14% remaining which usually gives her around 40km, she drove a total of maybe 18km when suddenly while driving the battery went down to 1% and the car gave an alert. She made it back home to our charging station (very slowly) and the car was fine after a charge. She insists that there were no warnings prior to the 1% warning (like I said, this is a second hand recollection of events) and that nothing out of the ordinary happened otherwise. Any ideas how this could've happened and what to do to avoid it?