When bowing in Shemoneh Esrei, when is one to lift his body back up, prior to saying G-d’s name, or while he is saying G-d’s name?
This matter is debated in the Poskim and Rishonim, and while some are accustomed to lift the body prior to saying G-d’s name, others are accustomed to lift the body as they recite G-d’s name, and so was the custom of the Rebbe as can be seen in the videos, and so is the opinion of Kabbala.

See Admur 113: 5; Brachos 12a; Poskim who rule to bow back up before saying Hashem’s name: Yerushalmi 1:5; Ravaya 1:39; Ritva and Rashbatz Brachos 12a; Opinion in Chidushei Rabbeinu Yehonason Melunil Brachos 12a; Opinion in Orchos Chaim Tefila 29; Siddur Yaavetz; Shulchan Hatahor 113; Chayeh Adam 23:3; Derech Hachaim; Chesed Lealafim 113; Kitzur SHU”A 18:11; Shaar Hatziyon 113:10; Shulchan Aruch Hamekutzar 16:21; Beir Moshe 3:21; Halacha Berura 113:7; Piskeiy Teshuvos 113:3; Poskim who rule to bow back up while saying Hashem’s name: Implication of Admur and Michaber 113; Levush 113:7; Rosh Yosef Brachos 12a; Hagahos Rav Avraham Azulaiy based on Kabala; Implication of Rashi Brachos ibid; 1st Opinion in Chidushei Rabbeinu Yehonason Melunil Brachos 12a; Opinion in Orchos Chaim Tefila 29; Abudarham; Birchas Yehuda 4:8 in implication of Rif, Rosh, and Michaber