i read your post about an hour before i reloaded 400 45 ACPs
i kept what you had written in my brain and watched my load and looked for any oddities.
i wanted to see if slight temp changes did anything to change my loads. it may or may not help your issue, but i figured a different loader or different processes may help you solve your issue with the bullets
i have used berrys bullets exclusively since i started re-loading, brass is "all the above" no aluminum, coated or weird brands
i have found some brass is heavier than the others,
room temp was 68 and bullets at start were 62
the dillion was room temp
my die opens the neck just enough to place the bullet on the case, with a just a touch of of enough bullet sliding past the neck to hold itself as the machine lifts the assembly up into the seating die
i had zero bullets drop or do any weird things
as i mentioned the resizing of the neck is only widened enough to sit the bullet on the case, enough to hold the bullet, but not let it go to seat depth until the press seats it.
i thought about your post and could only come up with my experience using the dillion square deal B
i check all settings at each start of load event, and once during the event at at around 400 rounds.
i check powder weights at 1st ten then at every reload of 100 primers.. i can say with my dillion;
once its set, it does not change any after 400 rounds. i use 400 as the point to clean up and recheck everything, not just powder or sizing, i mean everything,
thats what i like so much about it, once its set, your good for many rounds.
now at the end of 400 yesterday, my machine was still at room temp of 68. i am sure if the machine warmed up t say 75 or dropped to 40 it may have changed size just enough to maybe change things.
over my 20k plus reloads on this machine, i don't remember ever loading about 70 or below 65.
i use a micrometer non digital to measure OAL cartridge size, bullets etc and do measure completed cartridges at random as i wipe them down and put in the mm case
i use the less is more rule, on resizing brass to maximize longevity. i usually end up tossing brass that the primer pops out to easy,