Discrepancies between GA4 and UA event counts, even with identical tags and triggers, can happen and are often due to the way these platforms process and count events. For instance, one finding suggests that GA4 might only show transactions that have a value for the field user_pseudo_id, which only appears in the BigQuery data export. Transactions where this field is null might not show up in the GA4 UI, leading to lower count compared to UA. This could potentially explain the discrepancy you’re seeing. Using BigQuery to look at raw event data is recommended for more accurate event counting.