Error in WSFC Role while applying SQL 2016 CU7 in Multiple SQL instance environment
Is it normal while updating 2nd instance of SQL Server the 1st instance get interrupted while server involved in Availability Groups, or should we follow any particular method in this case to avoid any error as such.


No, it's not expected. The error, though, says it tried to bring the resource online and failed at least 3 times (by default, unless you changed this value). This leads me to believe that the instance was patched while it was a primary, which would of course fail while the service is offline for patching. If it wasn't a primary then you'll need to look into the SQL Server errorlog and the cluster log to understand what had happened.