I haven’t noticed that issue but overall I’m not very impressed w the iOS version and tend to use LP for MacOS and use FaceID (or even iCloud keychain) in iOS. I have LP Families w some nice features so that’s my primary reason for purchasing...
No problem on any of my devices. I use LastPass on iOS macOS and Windows. I’ve never had any issues with synchronization or any other issues. Been a LastPass user for years.
In iOS you can refresh the vault via settings/actions. macOS have LastPass as the app in focus, then choose file/refresh vault.