A small but known issue is that, on some of the galaxy watch models, messages will get sent a second time after a restart update or switch between Bluetooth and LTE connection.
I just updated this morning and was bombarded by hundreds of texts.
My solution was to go into settings then permission then message and disable permission for user history and message.
I don't use the watch to text and my default app on my phone is textra.
So that stopped the notification barrage and will in the future when changing between cell and Bluetooth at least.
Sadly the update changed the permissions this time which is why it happened.
Previously however updates didn't change the permissions and I didn't have the issues.
If you have any other info regarding this issue please let me know. I know it's not the best fix but it works.