UIProgressView keep going thinner when reloading tableview

Question

I have table view loading data from URL. I create custom cell containing UIProgressView with below values :

let slider : UIProgressView = cell1.contentView.viewWithTag(13) as! UIProgressView
slider.transform = slider.transform.scaledBy(x: 1, y: 0.5)

at first run it seem fine, and each time the app do self.tblview.reloadData(), UIProgressView getting thinner until disappear.

also, please see below screenshots : first time run

after 5 times reloading of tableview