I had a weird issue that keeps happening to me when I search an address on my apple watch series 3 with LTE on maps. When I select a destination and the GPS kicks in, it will still run in the background even after I closed it out. It manages to pop back up and run causing the watch battery to drain quickly. I've been able to replicate this issue everytime I select an address. The only way to fix this is to turn the watch off and back on or to keep closing the maps application maybe 10 plus times. This certainly feels like a bug in the watchos. I think I'll test this out with my wife's watch as well.