You could try replacing the cable that goes to that lug (or swap it out with another cable of similar length and see if the heat follows the cable.
See this article from trojanbattery.com, read under the "Improper Connector Assembly". Even if your cable terminals look good, some internal corrosion or other flaws can lead to high resistance.
https://www.trojanbattery.com/pdf/WP...Guide_0512.pdf