There's a couple of things to check. The ejector could be gunked up and stiff. To clean that without disassembly you can flush it out with Brake Kleen spray or Contact Cleaner and then place a drop of Rem Oil on it at the bolt face and use an empty case to work the oil in. Wipe off any excess oil.
If that doesn't take care of it then you need to remove the firing pin and clean it thoroughly. Do not disassemble the firing pin/spring, you don't need to. Clean it thoroughly with paint thinner then Contact Cleaner or BrakeKleen spray. Lightly coat the spring with Lithium White grease. Do not get any lubricant on the firing pin itself, it works best when dry.
There's video's on YouTube that show how to remove your Mark V firing pin.
Just looking at the fired case and the indent from the firing pin being slightly off center, I'm betting it's the ejector. I don't see the normal wear at the firing pin hole that is usually present with a bent firing pin. Weatherby ships the bolts with a lot of grease on them and if that's inside the bolt body it could be gunked up now and slowing down the firing pin. The firing pin could also not be tensioned correctly but that's something you shouldn't do yourself without the proper tools and gauges. If the strike tension is too great you could punch a hole in your primer and permanently mess up your bolt face. So, don't do it. Instead call Weatherby Consumer services.