Error returned from introspection endpoint: An error occurred while sending the request.

[unionthugface]

We have multiple applications using client credentials flow token introspection, communicating with a load-balanced solution using IdentityServer4; all of these are hosted in IIS. At least once/day, one of the initiating apps will start generating the error Error returned from introspection endpoint: An error occurred while sending the request with callsite IdentityModel.AspNetCore.OAuth2Introspection.OAuth2IntrospectionHandler.HandleAuthenticateAsync. No further exception is logged. Sometimes just one app will start generating this error repeatedly, indicating that the problem is not coming from the IdentityServer4 solution; other apps will have no trouble with token introspection at the same time. Occasionally, all apps connecting to the IdentityServer4 solution will start producing this error, but that is more rare. Failed request logs don't turn up anything, and neither does our APM. Clients have told us they are unable to use our app(s) while this is happening. It doesn't happen at the same time each day, and sometimes it happens multiple times per day. We have had no luck figuring out what could be going on. Any insight is greatly appreciated.