EDIT: It only took a week but I eventually found out the issue, primarily due to pure luck and another error with a more specific fix. The issue was with the connStr I had made, which for some reason on this machine gave me the error randomly of "System.ArgumentException: Keyword not supported: 'datasource'." during runtime. I then found out a fix for that was to rename the connStr as follows:
connStr = @"server = (server name); Initial Catalog = AutoTestDB; …