I promised to update this forum, but that thread has been inactive for other a month, so this is a Part II. We confirmed that the app was not passivation safe by disabling AM pooling. The procedure-based workaround did not solve the problem, and we couldn't find any code that was clearly non-passivation safe, so we are rebuiding the app. Sorry that we did not have enough time to debug the passivation safety issue; the knowledgebase could use more contributions about that. (Although maybe that means no one else is "lucky" enough to experience those issues).