"Confirmation #XXX was generated for this order." - not tracked in GA

[colinhall]

I have this open as a ticket with Shopify Support, but figured I'd keep a record of the issue here to a) see if anyone from the community has any thoughts and b) hopefully post any resolution from the Shopify side for anyone else facing this same issue.

The issue is that some orders aren't showing up in Google Analytics correctly, because our GA4 purchase event isn't firing properly (they come through as Transaction ID: not set). I looked into the orders which are affected, and the thing they have in common is a message in the order timeline saying "Confirmation #XXXX was generated for this order."

I can see the revenue tracked in GA4, but not as part of the purchase event, and it's missing all the additional data such as Order Name, items, etc. The checkout page is also tracked as:

https://domain.com/checkouts/co/xxx/thank_you

rather than the usual:

https://domain.com/xxx/checkouts/xxx/thank_you

Will update as I hear more, but would love to know if anyone has any ideas?