Runs of the flow's seem good, but in practice no message is received by the contact

hi

I built a scenario in the Make software, at the end of the scenario the custom field in ManyChat changes, and this should trigger Flow in ManyChat to send a message to the specific contact (a template message or a regular message depending on the time frames). The scenario runs one after the other for 7 contacts (7 contacts are supposed to get the flow start).
In manychat it seems that the number of runs of the flow increases, but in practice no message is sent. Sometimes one of the 7 messages is sent (to me, to the phone number of tests) but not to the other contacts.
Anyone have an idea why? There are no errors in the log view.
Is there any limit to starting Flow? Need to wait a few seconds?