Update Contact from Zapier to Keap Skips Records

I’ve noticed Keap skipping records in a small bulk Contact record update from Zapier. I’m updating a custom field in Keap with a code-generated value in Zapier. Keap is skipping about 50% of the records, updating only about half the contacts. This was a small batch update of >75 records. Has anyone else noticed something similar recently? Is there a better method for doing batch updates from Zapier to Keap?