We are noticing that when we ping out from our Routerboard in the evening especially when the bridge interface has 1500 to 2000 Packets per second running through it we get about 10% to 20% dropped pings.

However the Interface stats do not show any dropped packets?

. We are on a Fiber backbone and when we bypass the routerboard we get 0 dropped pings

We are typically pinging Google an Inside address and get the same results. It's only under load that we see significant missed pings.

Is this a concern?

I dont think thats normal, but that depends on several factors.

What routerboard you are using?