Does anyone have an idea what kind of issue this may be? I see there is sometimes a spike in the server side number of purchase events in CAPI, which also overstates the campaign performance.
My advise would be to comb through logs, maybe also enable request/response ones in the Fb tag, and/or connect our Logger tag.
You can gauge from that how often corresponding trigger events hit your sGTM and maybe find a pattern. Those CAPI spikes mean sGTM inbound spikes to trigger said CAPI. If you don’t find anything - you will anyway get a clear view of what was generated by sGTM