I have the exact same problem detailed above. When customers subscribe, because the fetch is by Order ID, only the first ticket is registered on google sheets. I have an event that goes over 4 days Thu, Fri, Sat, Sun all in one registration. I tried to create a second automation and this duplicated one of the days so I'm sure that wouldn't work. I tried add multiple rows but that only added the details in the booking and not the customer details. I am really stuck.
I wish the solution to Sajhussain above could be publicised here in the forum. Please help. I have now lost half of my signed up allowances and sleepless nights trying to solve this. I wish to request a reset of allowances please. Kindly reply ASAP as people are registering right left centre now. I have had to disable all flows that I had implemented.