One of the two most recent updates, 3.4.6 or 3.5 – I suspect the former – introduced a bug that breaks at least two of the meta key fields: plain_orders__edit_last and plain_orders__created_via. Appears to be caused by the prefix handling made for Origin support.
Implementing regression tests for the remaining meta key columns the plugin supports very likely may uncover additional ones. (_created_via was fixed by changing it from plain_orders__edit_last to plain_orders_edit_last; I was unable to get _edit_last to work).
Additionally, the change from using 0 to null/missing for customer_user key for handling guest orders without a user id should have been treated as a breaking change, and at the very least been announced in the changelog. Silently altering the way missing values are represented can and do have significant unwanted side effects when processing the export in data pipelines, as it did for me in this case.
WordPress version: 6.5.2
WooCommerce version: 8.8.2