UDP Port 500 is used in IPsec communications, without that you wouldn’t be able to establish a tunnel. Can you switch from IPsec to PepVPN/SpeedFusion instead? There are two ports required to be open for that (default UDP 4500 and TCP 32015 but can be changed) and that might help you pass the security scan.
I was suspecting that we needed those ports for it to work.
The IPsec Tunnels are connecting to service providers, that have Cisco devices on their end. Can PepVPN/SpeedFusion be used in that situation, or does their end have to also be using a Peplink?