Bizarre Flow error when deleting records that were queried: ENTITY_IS_DELETED

Question

I have a Platform-Event Triggered Flow which does the following:

1. After insert of a Platform Event record...
2. Get OpportunityLineItem records related to an Opportunity
3. If the result of the above query was not null (i.e. at least 1 record exists), delete all the records from the Collection above, and then create new line items.
4. If the result of the above query IS null, then don't try to delete any line items, just create new ones.

The problem: When testing this flow on an Opportunity record which has 1 line item, I'm getting the following error:

Error Occurred: The flow tried to delete these records: 00k2z000002co9wAAA. This error occurred: ENTITY_IS_DELETED: entity is deleted

There are 2 strange parts to this error:

1. If the record doesn't exist (it doesn't - I checked the database), why was it queried in the Get Element and attempted to be deleted??
2. The existing line item record that SHOULD be deleted by the flow has a completely different record ID. Where on earth is the record ID in the error even coming from?? -> 00k2z000002co9wAAA ... It's like some ghost record hanging around.

Notes:

• There are some existing triggers on Opportunity, but none that will fire for this event as far as I can tell
• There are no triggers or other automation on OpportunityLineItem