See Event Viewer System as well as Application log on Node 0 and 1 as well as logs in %VCS_HOME%\log. The most important cluster log file is engine_A.txt.
Extract from VCS admin guide:
To view log files
1. From the Control Panel, double-click Administrative Tools, then Event Viewer.
2.
Review the System Log to view LLT and GAB errors.
3.
Review the Application Log to view HAD errors.
HAD service is represented by the Veritas High Availability Engine (had.exe) in Services.
There is also a hashadow.exe process that monitors had.exe and restart had if it is stopped for some or other reason.
You should be able to find evidence in Event Viewer Application Log on node 1.
Also run 'hasys -display' from cmd on node 1.
Look for
EngineRestarted in output :
Indicates whether the VCS engine (HAD) was restarted by the hashadow process on a node in the cluster. The value 1 indicates that the engine was restarted; 0 indicates it was not restarted.