On my Macs I am using 1Password v6.8.9 - which is the last version of the v6 series. On iOS I am running v7.3.4 which is the latest as of July 21.
I initiate the WLAN syncing (over WiFi) on my Mac and sync that to my iPhone 7 and iPad 6 - both running iOS 12.3.1.
The app crashed on BOTH iOS devices when the sync process started. This was the first time this has ever happened. Both of my devices sent a crash report just a few minutes before July 21, 2:20am PDT.
iPhone 7 + iPad 6:
iOS 12.3.1 / 1PW v7.3.4
Mac mini + MacBook Pro:
macOS 10.14.5 / 1PW v6.8.9
1Password Version: 7.3.4 (iOS); 6.8.9 (Mac)
Extension Version: Not Provided
OS Version: iOS 12.3.1; macOS 10.14.5
Sync Type: WLAN over WiFi