Delivery addresses being wiped from orders

[cricket-hockey]

v1.7.6.5

About 2 months ago we suddenly started getting orders with no delivery address. It happens in about 1 in every 200 orders or so.

We get the Company Name, State and Country but not Address 1, Address 2, City or Postcode.

These are all required fields on our checkout so you can't checkout without them. So when the order gets passed to the payment provider (either PayPal or Stripe) these fields for some reason get wiped out. They don't appear in the payment processor's order either so the address cannot be checked for fraud.

Any idea what could be causing this? I have tried disabling some modules I installed around that time but it didn't help, and it's odd that it happens so randomly and not to all orders.