Template variables keep changing to default?

I noticed that if I change the template variables in the Templates/Portfolio view (either in the code directly or in the template preview/editor), those variables will change back to default at some point in the future. I didn't measure exactly how long does it take to go back to the default, but basically every time I go back to my website and check it, the variables are default. I can instantly see it cause the main variable I'm trying to change is the "Thumbnail size". Here's my website: https://lotafak.blot.im/

Please advise! Thank you