A SQL Server technology that supports the creation, management, and delivery of both traditional, paper-oriented reports and interactive, web-based reports.
Worth to also check: After you have changed the global rsreportserver.config for the delimiter, did the report server app pool make a recycle? Because such a config change is restarting the service, so the first run(s) after that are having additional cold-start cost on top of the normal query time — this could explain why it is sometimes timing out and sometimes not, independent from the 3600s settings you have already adjusted. You can check the ReportServerService trace log timestamp of the failing run against the timestamp of the config change / app pool start, to confirm this.