Error when creating subscription on linked report

I'm not sure if this is the appropriate place to put this as it's not a PBI report problem per se, but we are running PBI Report Server so I thought I would start here.

We are getting the dreaded, vague "Something went wrong. Please try again later." error when trying to create a subscription on the linked version of an SSRS report. This happens whenever I try to set the value of a parameter. The error does not occur on when running the report either normally or when creating a subscription on the "base" report, only when it is a linked report.

I've managed to reproduce the error by creating a very simple report. The main thing is that the report must have a cascading parameter. The error occurs as soon as I set the value of the first parameter in the subscription.

We have upgraded to the March 2018 PBIRS release, but the same problem was happening with the October 2017 release as well.

Any thoughts or ideas would be most helpful as we have a lot of reports using the exact scenario above (linked, cascading parameters with subscriptions) that worked fine in SSRS 2008/R2 and are still running, but can no longer be edited or new subscriptions created since we upgraded.