Photo count mismatch on iCloud.com

I use iCloud Photos on all my Apple devices and it worked pretty well. However, I found the number of photos doesn’t match between Photos app (cross all devices) and iCloud.com.

-> iPhone: 11779

-> iPad: 11779

-> MacBook: 11779

-> iCloud.com: 11778*

Since all photos are synced, I found out the specific photo (on my devices) which disappeared from iCloud.com, and noticed that it shows already synced (cloud with a tick), too.

No matter I switch off/on the iCloud photos, I cannot force it re-synced again, and I still cannot see it on iCloud.com. Is there any way to solve the problem? Thanks.

iPhone XR / iOS 15.3.1

iPad 5th / iPadOS 15.3.1

MacBook Air / macOS 12.2.1