Sorry to hear that, about your experience with the recent updates on your Samsung Galaxy A51 having lagging issues with the camera and we apologize for the inconvenience it caused you.
If it still doesn't work, you can submit an error report through Samsung Members app as follows:
Step 1. Long press Samsung Members icon on Apps screen and tap Error reports.
Step 2. Tap OK on agreement popup to send system log data.
Step 3. Select Symptom category "Camera".
Step 4. Describe the problem in details and SEND.
For more assistance, you may contact us on our online Samsung support channels below.