Night Mode Camera

I got a iphone 12, and whenever i go into a semi, or fairly dark room. The night mode indicator on the top left shows how long it'll be taking the photo, usually 2 or 3 seconds. but on my phone, it just spazzes numbers 1, 2 and 3. like it cannot decide how long it'll be taking the night mode picture. i'm wondering if it's an issue or it's just normal. Also on the ultra wide camera, it doesn't rapidly spaz.