i would think that the pack wheels being loose is a good thing. this gives the pack wheels movement to roll and compack the seeds in uneven ground.
I have an old (i think its a brillion brand 8ft)
it does a great job, even has a busted wheel or two, but seed always come up good after running over them with the packer.
these old machines were designed to be a bit loose.
worth there weight in gold when planting seed.