Xcode Storyboard Fail to show (render) ViewControllers (The agent crashed)

Question

I'm running Xcode Version 10.2.1 (10E1001) on MacBook Pro 2016

• Processor: 2.6 GHz Intel Core i7
• Memory: 16 GB 2133 MHz LPDDR3
• Graphic: Radeon Pro 450 2 GB and Intel HD Graphics 530 1536 MB
• Storage: 256GB SSD

• Free Storage: 45GB SSD

  When i try to open storyboards i see a Storyboard with transparent ViewControllers but those ViewControllers already have UIViews and backgrounds but Xcode doesn't show,This remains for more than 20 minutes, then UIViews appear

This is how my @IBInspectable class looks like:

import Foundation
import UIKit

@IBDesignable
class BorderButton: UIButton {

    @IBInspectable var cornerRadius: CGFloat = 0 {
        didSet {
            layer.cornerRadius = cornerRadius
            layer.masksToBounds = cornerRadius > 0
        }
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

}

Im getting error The agent crashed:

See picture below:

What i've done:

• Cleaning build folder
• Removing Derived Data
• Close Xcode and re open
• Free up ram
• Solutions from this question

but none of above worked for me.