private fields showing on invoice

First of all, I must say this is a great plugin. I made really beautiful and useful automatically generated pdf invoices.

But I have a problem with some extra description in automatically generated pdf.
I use the AeroCheckout plugin, which has some private fields.
Under item, there are additional fields:
_wfacp_product: 1
_wfacp_product_key: wfacp_5d9d991800303

When I contacted AeroCheckout support, I get this answer:
The keys are private keys as they start with an underscore ( _ ) and they should not be picked up by third-party code.

This thread talks about it as well:

The underscore prefix is private, these meta fields will be hidden and will not be shown as custom fields in the post backend screens. Those meta fields without the underscore prefix are public fields and show up as custom fields in the post screens

Source: https://wordpress.stackexchange.com/questions/183858/difference-between-meta-keys-with-and-without

I hope that some solution is found because I really want to continue using your plugin.