By default, bitcoin core has minRelayTxFee of '0.00001000' or 1000 satoshi per 1000 bytes.

This should be the same as 250 satoshi per kiloweight, but it's not since it internally uses vbytes (which rounds up). As a result, modern (segwit-only) software must perform hacks to ensure that it generates transactions which propagate, and authors write angsty, whiny commit messages:

ElementsProject/lightning@2e687b9

What behavior did you expect?

Transactions with exactly 250 satoshi per kilosipa should propagate.

What was the actual behavior?

Only one in four transactions like this will propagate, the rest will be rejected.