One Calendar slow on Android

One Calendar became very sluggish on my Android, and on my wife's Android, phones a few days ago.  The app is slow to open and goes into a long sync cycle when the calendar display first appears.  After that he app is also very slow to change displays, for example from list to week.

We are on Android 12, and this problem occurred at about the same time that an Android security update was applied on February 5.