"...typically a sign of low pressure..." And excessive pressure and bad headspace. Neither of which is likely. Unless you've changed the bolt without using headspace guages.
13.5 grains of H110 is .5 of a grain below minimum. Hodgdon gives 14.0 to 15.0 for a 110 grain jacketed bullet. That half grain shouldn't cause primers to back out. Try loading some commercial brass with 14.0. You should work up the load though.
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