For anyone still interested or affected by this:
Latest from Groupcall:
"When an MIS makes changes to how data is displayed within their system we must release an update to support those changes. In this instance we weren’t made aware of the changes until affected schools reported them to us, however, I’m now pleased to confirm that the development work with iSAMS has been completed and the underlying issue has now been resolved and the data will automatically sync within the next 12 hours.
Could you please review the data tomorrow once the sync has completed and let us know if you encounter any further issues or discrepancies?
Thank you for your patience and understanding while we worked to resolve this matter with iSAMS."
The latest fix is syncing data, but the weeks are out of sync if you have multiple week timetables, so not there yet.
Groupcall still blaming iSAMS, iSAMS still blaming Groupcall...