2.4GHz is more susceptible to interference for a few reasons. Primarily there are only 3 non overlapping channels (1,6,11), so the AP doesn't have much to choose from. Certain environments are worse than others, such as multi tenanted buildings as you'll find a lot of other APs not just your own using the same channel. APs aren't the only issue, mobile hotspots will pop up on the 2.4GHz, then you also have other devices such as bluetooth and also microwaves using this. Power levels can also inadvertently cause CRC errors due to a hidden node issue along with multipath.
5GHz is still susceptible to interference but you have many more channels to choose from, hence you're more likely to be able to move away from the interference source.
Is that -64 neighbor on the same channel as the AP you were looking at?
