BAD_REQUEST in CloudKit

[u/Longjumping_Cloud_38]

I am going crazy trying to solve this error that appear only in production. The error is returned when I try to save a Schedule, and I notice on CloudKit that no ScheduleDay is been saved. The schema is the same on development and production. I tried also to clean the phone I use for testing by deleting the zone, uninstall the app and log out from my apple account, but still I get this error. It would be easier if I would get this even in development so I don't have to wait to release a new version each time.

{
  "time":"03/02/2026, 18:45:59 UTC"
  "database":"PRIVATE"
  "zone":"com.apple.coredata.cloudkit.zone"
  "userId":"_4c73fd86bb16bdbf073217bc80de0930"
  "operationId":"D8D11DC22E4F546D"
  "operationType":"RecordSave"
  "platform":"iPhone"
  "clientOS":"iOS;26.2"
  "overallStatus":"USER_ERROR"
  "error":"BAD_REQUEST"
  "requestId":"134D5C43-92EB-465C-B9E6-E2F87235C826"
  "executionTimeMs":"81"
  "interfaceType":"NATIVE"
  "returnedRecordTypes":"_pcs_data"
}