Do you guys have any "Line Item" fields dropping to the Google Sheet? That can cause multiple rows to be created because of the nature of line items.
Line items are seen mostly in financial context and equivalent to a receipt from the grocery store.
If I buy an apple, an orange and a banana, costing $0.50, $0.75 and $0.50 and decided to write the information from the receipt to Google sheets, it would drop as three rows:
Name. Item. Qty. Price.
Steven. Bananna. 1. $0.50
Steven. Apple. 1. $0.50
Steven. Orange. 1. $0.75
I didn't see you mention any line item
fields but wanted to mention it. There are many ways around this using Zapier's formatter action. You can find more details here: https://zapier.com/apps/formatter/help
I'm happy to help if you have specific questions. I can't think of any other reasons this would happen, especially because Zapier remembers what data has already been processed. It could be a glitch, like you said but I haven't experienced it (yet!).