Information Request for US Shipment?

Are these requests sent randomly or is someone specifically initiating it?

For instance, let's say I sent an item that I specified is 10 by 10 inches big.

I've sent the same item 5 times to the US. 4 times they cleared customs all fine. But randomly I got an email maybe 15 minutes after it was scanned after a courier picked it up from a dropbox and the email said they needed to know the item measurements and what unit of measurement was used.

Meanwhile the info is on the invoice so why do I need to resubmit it for this one shipment but all my others didn't?