I am starting a new thread as this might also occur if someone installs the patch below and also as this patch is going into the next release.
This is a continuation of Upgrade from 5.65.1 to 5.74.0 - Error "Expected to find one Participant record, but there were zero." when registering for an event
Tha patch that was suggested https://patch-diff.githubusercontent.com/raw/civicrm/civicrm-core/pull/30392.patch, seems to partially work as the PayPal payment goes thru and we do receive the funds. However we have noticed that the new registered participant is not being added to the event. When we look at the new participant record -in the Event tab -it shows that the participant has the status as "Pending (incomplete transaction)".
Any help what we do here will be greatly appreciated. Thx.