As "better_half" said "crashing" is too vague a term for diagnosis, we need the symptoms.
Having said that ... the most likely crash is that it is running out of memory.
When you unpaired and then installed the update, it is likely that you got a lot of default settings for things like Audio Books, Mail, Music, Photos, Podcasts ... They probably all start off set to "Mirror my iPhone". So your watch has probably filled itself with stuff that you had previously turned off.
So I would suggest going to the Watch app on your phone and selecting General/About and look for "Capacity" and "Available". If "Available" is down to a few Mb or even zero! then that is your problem.
Solution: in the Watch app, go through the settings for each of the apps that download media and change their setting from "Mirror your iPhone" to the setting that will use least memory while still meeting your needs. For example, for Music, you might want to create a small playlist (in Music on your iPhone) and set that to be the thing downloaded. Similarly one album of important images in Photos etc etc