We had the same issue, but it was over by 10-20% in our case. Discussed this with them multiple times, and the last response I got was:
"I've checked in with our engineering teams, and we unfortunately don't yet have a fix or timeline to share here, though we have made additional progress on scoping a path forward. It's extremely complex on our end, as existing data models don't have the required information in place to make the change here, and we'd need to scope how to add that and backfill data (which we're approaching, but again, no timeline to share as of now)."
Obviously I don't know anything about them internally, but if I can export the data as a CSV-file, and then calculate the MRR myself in GSheets, then what data needs to be backfilled? The data is already available to properly calculate it.
My interpretation of backfilling here is that they need to architect the data in a different way to be able to have all the information needed to calculate the MRR correctly. Then once the data is modelled how they need it, they have to backfill the new model. Basically like your export to csv step. I'm sure the data that fills your csv export is coming in from a dozen different tables and sources.
"I've checked in with our engineering teams, and we unfortunately don't yet have a fix or timeline to share here, though we have made additional progress on scoping a path forward. It's extremely complex on our end, as existing data models don't have the required information in place to make the change here, and we'd need to scope how to add that and backfill data (which we're approaching, but again, no timeline to share as of now)."
Obviously I don't know anything about them internally, but if I can export the data as a CSV-file, and then calculate the MRR myself in GSheets, then what data needs to be backfilled? The data is already available to properly calculate it.