Invoice updating issue for more than 20 invoices in a batch

Hello, I have a problem related to this endpoint:
/crm/objects/v3/invoices/batch/update

When I attempt to batch update more than 20 invoices at a time I get the following error:

{“status”:”error”,”message”:”There was an error processing the request.”,”correlationId”:”942e1f44-64d2-444c-b010-f138568a639c”,”category”:”INTERNAL_ERROR”}

Does anyone have an idea why this is?

I am guessing its a bug within the API because the lesser invoices updated in batch the less I see it.