During the shipment creation, I'm seeing this timezone issue. I am wondering which module I should look into and debug
The invalid TZ in question is "PST". I think it should be a full TZ like "America/New_York"
Check in PREF_PROP_LIST in table USERS. You probably have a bad value in there. You can actually just nullify that column for the cur user, log out, and log back in to resolve it.
OK - at this point i'd say file a JIRA. Include all the detailed instructions for reproducing it, including URL, user/password, role and steps to reach the error.