Explanation
According to this question, uRPF is running in strict mode because packets are dropped even when that route exists in the routing table. Maybe packets are dropped because the receiving interface is different from the interface the local router uses to send packets to that destination.
The ip verify unicast source reachable-via rx command enables Unicast RPF in strict mode.
To enable loose mode, administrators can use the any option (ip verify unicast source reachable-via any). In loose mode, it doesn't matter if we use this interface to reach the source or not.

The allow-default option allows the use of the default
route in the source verification process.