I dunno if you have easy access to get on a call with someone at Blue Prism, but that may be a good idea for troubleshooting this. If you try to handle it over the forum, it's gonna take you days or weeks.
So, for the problem itself... I feel your pain. Scheduler can be tricky, and half the time I don't know what changes fixed the issues. I believe that the error you're getting is a fairly generic error. You may want to describe your environment and things so that people can give specific suggestions. For example, how many RRs, how many app servers, is there a load balancer involved, is this on prem or cloud? And anything else you can think of.
Also take a look at the Support Article. You may have already tried everything there, but I figured I'd mention it:
http://portal.blueprism.com/customer-support/support-center#/path/1139600832
Lots of people have issues like that so I imagine more people will comment with some suggestions.
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Dave Morris
Cano Ai
Atlanta, GA
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Dave Morris, 3Ci at Southern Company