1) Why does Shmuel gather the people in Mizpeh? Is it potentially connected to a previous event in Jewish history? See Yehoshua 11:3.
2) Am Yisrael’s teshuva certainly relates to the sins of idolatry (pesukim 3-4). Did they repent from other transgressions as well? See pasuk 6 and R. Yosef Kara.
מהר”י קרא פרק ז פסוק ו וישפוט שמואל את בני ישראל: בין איש לרעהו על עסקי ממון שביניהן ועבירות שבידם
3) We noted in perek 4 that the people may have mistakenly thought of the aron as an independent magical force and did not view God as their savior. Which pesukim in our chapter show that they now understand that victory depends upon Hashem?
4) Arguably the seventh chapter goes out of its way to make us remember the fourth chapter. Compare the place mentioned in 4:1 with 7:12. For more parallels, see R. Bazak. http://etzion.org.il/en/11-chapter-7-israel-under-shmuels-leadership. This would clearly support the idea in our previous paragraph.