In all of Adobe's documentation, they state that TransactionID's must be unique. But they also state that if multiple TransactionID's are uploaded during the same visit, the snapshot that will be saved is of the last TransactionID uploaded.
So my question is, if we upload the same TransactionID across multiple visits. When we upload offline events to that TransactionID, will the events be tied back to multiple visits, and if this is the case, would uploading $25 of revenue end up showing up as $100 if it ends up being tied to 4 visits with the same Transaction ID? Or would the offline events just be attributed to the most recent visit with that Transaction ID?
The reason we need to know is that we are using our in-app user ID as the transactionID, and while we could pre-pend the userID with a unique event identifier to keep the transacitonID unique, our app data that we are uploading to analytics will not have access to that unique event identifier, so we will only be able to upload the in-app user ID to adobe as the transactionID.
So I just barely finished testing this by uploading transactionIDs to 200 users for whom we recorded multiple transactionIDs, and 100% of the time the transactionID data was tied back to the first visit where the transactionID existed. Which is actually ideal for our specific use case
Let me preface this with the fact that this goes directly against transactionID best practices, and if it doesn't work, I'm afraid there's not much that can be done.
With that said, based on my knowledge of how transactionID's work, I speculate it would only tie to the most recent transactionID definition. You are more than welcome to try it on your end and share your results, though!