Reverse path check means, firewall is expecting that source IP to come from one interface but the packet is coming from different interface.
For example, execute this command:
get router info routing-table details <source-ip>
You will get to know from which interface firewall is expecting to come traffic from for this source IP.
If there is no route for the interface on which traffic is coming, create one static route for that source IP towards that interface on which traffic is coming