Never observed erection difficulties related with ball busting. The excitement seems so high it overcomes potential weaknesses.
I have now been into passive ball busting for more than thirty years and my hard-on(s) are always fully hard for a long long time. I must add my partner always stopped working with my balls when I was passing out: She said She wanted me to feel each of Her actions. The other effect of such a rule was introducing a kind of safety limit. Sometimes, when I was out but still fully hard, She happened to mount me and get Herself off over me ***********.
On the other hand (if I may say so!), I have (once) been severely cock busted (trode on by a heavy Lady when fully hard) and experienced that time a total impotence for several days!
Hope to have added something to the debate!