For Oracle Forms 11gR2 and 12c protected by OAM using WebGate, there are known reports where users may encounter errors after being logged into the application for 60 minutes:
FRM-92091: Unexpected fatal error in client-side Java code
FRM-92102: A network error or server failure has occurred
The reason for these errors is because the “Token Validity Period” is being reached. This is a setting configured in the webgate agent. By default, this parameter is set to 60 minutes or 1 hour. This means that regardless if the end user has been using Forms for a full hour or if the user has left his or her Forms session idle for an hour, a timeout will occur. To solve this problem, the Token Validity Period setting in the webgate agent will need to be increased to a value (in minutes) where end users will not encounter these errors (i.e. 480 minutes (8 hours) or 540 minutes (9 hours)). You will need to determine the amount of time before this timeout occurs.
NOTE: When you update the Token Validity Period for the webgate, you will need to redeploy the WebGate files generated in the $OAM_DOMAIN_HOME/output/<WebGateAgentName> directory into the OHS home’s webgate/conf folder as well as restart OHS.
After making the change above, the errors should no longer occur once 60 minutes has passed.
Source: Oracle Support Document ID 2178936.1