I once had an issue where a Palo would commit fine until I started using the certificates it had installed. (e.g. added a GlobalProtect Portal).

At that point I would fail to commit with the message

Error: Certificate 'cert name' failed to load: Internal memory error.

I noticed that the firewall was using almost 100% RAM. A reboot fixed the issue.

If you load partial configuration in Panorama and then commit, you may find you get the following error message

    Validation Error:
    template -> {TEMPLATE_NAME} is missing 'settings'
    template is invalid

The solution is to go to Panorama→Templates. Open the template and set “Default VSYS” from 'none' to 'vsys1'.

This issue often occurs when you create the Template from a CLI command

set template NAME config vsys vsys1

without also running the command

set template NAME settings default-vsys vsys1