Zend certified PHP/Magento developer

Magento checkout page intermittently returning 404 error

We are on magento community 2.4.0 and for the past couple of months, (occasional) transactions have resulted in 404 error after checkout.
We don’t get any notification of an order.
I looked on stack exchange and someone reported this with mageonto 2.3 but I wonder if the same issue could be causing our problem on 2.4 ?
I am unsure since most customers checkout without any issue but it seems to be happening more often in the past couple of weeks.
We use paypal as our payment processor – not sure if that’s relevant.
Thank you for any help!