On the off-chance they are an eG Enterprise customer - beyond Citrix / RDSH / AVD EUC we do web and app server monitoring and code level root-causing (aimed at the frontline / infra admin not a dev tool - GUI no command lines 😄 ).
https://www.eginnovations.com/supported-technologies/microsoft-net-monitoring they could just transfer a license or two across to get access to the .NET errors to confirm if code / misconfig or ask their account manager for a trial. Most enterprise monitoring tools with even basic app monitoring should be able to do something to diagnose it - so if not eG ask your monitoring vendor of choice!