I was updating to 10.3.1 and found that my AWU2 was stuck at "preparing" for several hours. This apparently is a known issue and the fix has been documented on this forum and at Apple support. As with most all of such issues it was a learning experience. I know how to delete the update file in the Apple Watch app, and how to do a hard reset on the Watch. Both of which are spelled out in Apple support. This was probably caused by my obsession with updates. I have it set to do them automatically but I never wait that long.