Sync Troubles with Desk

Hello everyone! Our company is new-ish to Zoho. We have Desk set up for support tickets for assisting our clients. We recently added CRM for communication and marketing. We set up a two-way sync between them. Only some data (accounts, contacts, etc.) has synced from Desk to CRM. For example: Desk shows 50,403 contacts but CRM only shows 8,323. The failure log keeps showing "INCORRECT_API_PARAMETER" on failed contact syncs. We have double checked all the map fields. We would appreciate any ideas to fix the issue!