Got Golem and Machamp through trade and i have no pokedex entries for them i have Alakazams though I fixed it i had to be the one evolving the pokemon to get the entry
Yes we have seen this on a very few occasion but not quite enough proof to look into it. It's because it's a trade evolution.
Definitely a bug.. what I do is trade them to another person and don't have them evolve then have that person trade them back to me and let them evolve.
That could work; it probably doesn't register it during the trade. (maybe the server thinks it's the other players Pokemon still.