Mazandarani believed in incompleteness of the uthmani mushaf

 Hadith#28 

Quran which was sent down by Jibril was 17000 verses long.

I(mazandarani) say: That which exceeds in verses of that what is written in hadith was removed through alteration and that some Quran was removed and altered is accordingly proven in our ways in mutawatir form as it becomes clear to those who read our books from beginning to the end.”

📚Sharh Usool Al Kafi V11,P87-88