It's hard to explain but no matter the placement of the source block, the piston will get powered and will never turn off unless updated. I saw a similar problem that said it was resolved but it was exactly my problem from what I saw in it's description and screenshots.

MC-179036 Said post is this.

In any case, I'm not entirely sure this is right but I thought it was in need of a good look at.

Here is a video to help understand easier and how to recreate it. I'm also bad at explaining things so it's good if you just want a quick look.
https://youtu.be/kDvYeEZJ1p8 This one shows somethings I forgot in the second one.(below this link.)

https://youtu.be/82_CwPT85dI