Those dropped packets are not normal - but it looks like those are all packets being dropped by a secondary router firewall after they've been forwarded without NAT by the primary router. Note that the destination on all those packets is the same (your WAN address I assume).
It looks like double NAT, but double NAT works for some people, and that does look extreme - have you changed the default syslog from its notice/debug defaults by any chance?
Maybe a rough hand-drawn diagram of what you have in place would make things clearer for us!
*I don't have a single such drop in my entire (current) syslog - plenty of dropbear instances though!
I only learn by making mistakes and owning up to them - boy do I learn a lot!
