2006 chevy cobalt T-stat issue

I have a 2006 Chevy Cobalt with 60K miles. I got it a year ago with 30K.
A month ago I got a CEL and the coolant temp was only showing 150 after a 50 miles commute. So i change the T-stat and the problem went away. Now a month and 4K later it is going the same thing. Is i possible that I got a faulty t-stat?
The CEL code both times was a P0128.
I don’t recall the brand of replacement t-stat that I used I know know I want a Stant brand and there were non and my parts place so i have to use a brand that I did not know (It was made in Israeli, not china, so i was hoping for a better quality)

Edit: Currently the temp is running about 175 to 185….but it did take about 15 miles for it to get that warm.