Hi Sanjay,
Please check in your tag manager and with your developers for any releases made around 25th Jan.
Analyze those releases for functions that can affect your page names.
If there is rise in some values there would be drop in others. check for the urls the values for which have gone down.
Debug the urls that have gone missing after 25th
If you can share the url here then contributors can debug it and help you
Best,
Sanmeet Singh Walia