Taking a hint from this post (https://virtualnomadblog.com/2018/07/26/vsphere-6-5-failed-to-deploy-ovf-package-from-the-content-library/ ), I've resolved this problem.
When cloning the template to the Content Library in the primary vCenter, I selected "Include extra configuration". By default this is not checked.
After the template syncs to the secondary vCenter's Content Library, it deploys successfully into the vCenter. There is still a warning during deployment, though its little different (more extra configurations). I don't know why checking that box resolved the problem, but it does.
