It shouldn't be related to reject or drop policy, both will deny connection, the difference is whether packet will be dropped silently or not. Interestingly, however, there does not seem to be any matches when it comes to any of these rules (besides first and last). Do you have some other rules, for example DMZ (port forward all ports to a single host) or anything that would match and bypass traffic rules in general?
Could you post all of the /etc/config/firewall file? Might be able to spot something from there.