I don't understand your question. This makes no sense:
I can't seem to keep my racket angle constant it just closes all of a sudden and makes my shot inconsistent. So does anyone here have any advice or tips in order to keep the racket angle consistent
Who do you think is holding your bat and making it move? If you think your stroke is wrong, then fix it. Fix it = stop doing the same thing over and over again. Do something different until it's right. What do you expect from us exactly? Or you want to keep doing it wrong but suddenly get a good outcome for no reason?
I'm being harsh because I believe it to be the more helpful answer here.
Ask somebody to have a knock with you (or hit against a wall or folded table),
very slowly so that it is comfortable for you to correct your stroke, and keep doing simple, controlled strokes until it becomes second nature, increasing the pace as you go.
From your video it is very hard to comment on your original post. It's 10s long, I'm not sure what we get to see. Maybe the format of the video just harms you. What comes to mind instantly are your grip, your stance and your flip-flops.
Anyway, if you struggle with control and racket angle on your backhand, maybe just work on your flat backhand as shown in here
https://youtu.be/92NWiTyfc4k?t=11m37s (he's doing it with shakehand a bit earlier in the video - by the way, there are a lot of good videos with Kim Taek Soo and Yu Nam Kyu showing some basics and more while visiting clubs, including many common mistakes... it's all in Korean but still useful without translation) or there
https://youtu.be/oZ3P95YWR9o Don't worry about spinning, drives/loops, playing flat is worth a lot of points too.