Another thing you could do is measure in a more granular way—ask for NPS about particular sessions. You could do this after each session or at the end of each day. This would help you narrow down what sessions are and are not working, and why.
You do have to be careful not to overburden people by asking them for too much detailed feedback too frequently, otherwise they’ll get survey fatigue and the quality of responses will markedly decline. Hence, I would resist the temptation to ask more than 1-2 questions about any particular session. If there are any that are markedly well/poorly received, you can follow up on those later.
Another thing you could do is measure in a more granular way—ask for NPS about particular sessions. You could do this after each session or at the end of each day. This would help you narrow down what sessions are and are not working, and why.
You do have to be careful not to overburden people by asking them for too much detailed feedback too frequently, otherwise they’ll get survey fatigue and the quality of responses will markedly decline. Hence, I would resist the temptation to ask more than 1-2 questions about any particular session. If there are any that are markedly well/poorly received, you can follow up on those later.