Siemens slow reconnection


I am using S7-1515 plc , i have used 26k tags, know i have facing issue like, when i have browse new tag from plc or edit same tag then tag value shown bad not found. That time i seen my opc connection shown connected and plc aslo connected.
We have using Ignition 8.1.37 V currently.
Previously we didnt seen that issue , but past 7-8 days we have facing daily same issue.
After restaring my PC then after half an hour to 2 hour all tags will conected.
We didn't undaustand how to resolve it.
Please suggest better solution.

{ I moved your post, as where you commented was purely a Rockwell discussion. }

Please provide more information, especially whether you are using IA's native driver or the 1500's built-in OPC UA server.