So it looks like the problem was on my side....
I was pulling a batch of events from "/errors" resource, which was pulling errors that were not necessarily "unresolved". So my script was passing in a batch of Ids to be marked as "resolved", it's just that I was passing in ids for events that had already been resolved.
I changed the URL to "/errors?status=unresolved" (or something similar, I don't have my code in front of me right now), which would then return only unresolved errors. I then looped through these and passed the list of ids into the "/errors/resolve" with a patch and everything started working just fine.
So first off... It was totally my fault. :)
But secondly, I was really only able to find this by running Fiddler and snooping through the network traffic that ServicePulse was sending to ServiceControl as well as searching through the source code on ServiceControl in GitHub. If this had some documentation around it with how to query the different resources or how to send in PATCH commands it would be a little easier.
Again, I'm making an assumption that there will be some documentation on this in the future, I'm just being impatient and want it now. :)
-Jesse