FortiGate and Solarwinds Max Backup Errors

Recently, several servers behind a firewall policy with default web filtering, default AV filtering, SSL Certificate Inspection and HTTP started failing their backups to a cloud provider.  The cloud provider responded blaming the FortiGate because it was replacing their certificate with the Fortinet certificate.  My understanding is that this is common behaviour for the FortiGate, and furthermore, why did the other servers behind the same firewall policy, complete successfully?  Additionally, the Fortinet certificate would be placed on all HTTPS traffic, right?  Could you some clarification here.  This is a FortiGate 200E in a Cluster Configuration.