Re: Primer backout problems
Doing a quick check of Hodgen's load data, your load is just fine. They list 43.5 grs H4895 as a max load with a 168 gr bullet.
There are so many variables with reloading it's difficult to diagnose a problem to a single cause. Backed out primers are "normally" an indication of a light load. You also mentioned that some primers are flattened?, which could be an indication of a hot load. Since the load you are using is less than a max load, but you're seeing both pushed back primers and flattened primers with the same load, my first suspect would be uniformity. My second suspect would be the brass. Here's a few ideas of what I would check:
How do you measure your powder for each load? Are you weighing each load or dispensing from a powder measure? You should probably carfully weigh each load.
Are you using a hand priming tool or using the ram on the press to seat the primers? You will easily feel the difference between a normal and a loose primer pocket using a hand tool. You may want to try a different brand of primers, brass, or both.
Are you checking case length and trimming to a uniform length? If crimping bullets this is critical for uniformity.
Is bullet seating depth uniform? Touching the lands, just back from the lands or set to recommended OAL?
How does the accuracy of your handloads compare to factory ammo?
Do you have a chronograph? Measuring your velocities may be the best indication of how uniform your loads are and a low velocity would also show you if this load just happens to be very light in your particular rifle.
These are just a few ideas to get you started. Pushed back primers wouldn't overly concern me, but flatttened primers definitely get my attention, so be careful.