I have a subscription setup to run a Crystal Report and export it as a PDF to a folder on the server. Manually the report runs and can be exported to PDF but the subscription errors our with "Operation illegal on linked parameter." shown on the history tab.
There may have been a sub report at one time as I can see a data connection to a sub report in Set Data source Location -> Current Data Source. Don't see a way to delete it though.
I started deleting objects one at a time off the report and found there was an unused sub report that was hiding behind another object. I Deleted the sub report and now the subscription is working as expected.