Wfm api 500 error during bulk schedule upload

Ran into a weird issue today with the wfm scheduling api. pushing 500 agents via post /api/v2/wfm/schedules in a single batch returns a 500 internal server error. smaller batches of 50 work fine. the payload matches the schema exactly. is there a hard limit on concurrent writes for this endpoint? seeing this in us-east-1 env.