Unless someone is saying they experienced a hang-fire situation or a squib load due to the cold, it isn't the primer that was the problem. Either the primer went off or it didn't--they don't really have a halfway point caused by cold.
If the primer did truly ignite, then a small flash hole is not going to hold back the ignition of the powder to the extent that the powder would not ignite at all.
Something else happened in those scenarios that are not due to a small flash hole.
