I had the same issue after back housing replacement, this post actually helped me a lot. Another guy mentioned that he has the same problem after charge port replacement. Eventually figured out that it was the charging port that came with the new back housing. I carefully removed the old port and put that one and it’s working fine.
One thing I noticed that the original charging port comes in 2 pieces and the pre-installed one was only in 1 piece, two pieces were soldered together which was probably creating this weird power glitch!
Hope this helps, good luck!