Xcode 10 Faulty Interface Builder

I do not experience those problems, using XCode 10GM. Now, XCode 10 has been released, is it the on you use ?

I use the version downloadable from the App Store

In the project you converted, have you external libraries or frameworks ?

It has no external libraries or frameworks. This error appears to happen when I uninstall a uiview with constraints. Here's a snippet from the bug log:

Failed to update scene 'W2x-hd-xYC' with IBLayoutConstraint (x30), IBUIViewAutolayoutGuide (x1), UIButton (x4), UICollectionReusableView (x1), UICollectionView (x1), UICollectionViewCell (x1), UICollectionViewFlowLayout (x1), UIImageView (x3), UILabel (x2), UIView (x3), and UIViewController (x1).

Exception reason: ASSERTION FAILURE: representedFirstView

Reason: Should have found represented view for first item <UIView: 0x7fe7f7c785d0; frame = (16 16; 704 382); clipsToBounds = YES; autoresize = RM+BM; layer = <CALayer: 0x7fe7f7c787b0>> for <IBLayoutConstraint: 0x7fe7f7f1ac40> UIView[0x7fe7f7c785d0].Trailing = IBUIViewAutolayoutGuide[0x7fe7f7f1a6e0].Trailing - 16.000000 containingView={<UIView:0x7fe7f7f1a980>} scoreVector=<Default, 20.00, 2, Tr, Tr, 1000.00, =>, roundingAdjustment=0

This error appears to happen when I uninstall a uiview with constraints.

Do you mean uninstall in IB or through code ?

Are the constraints connected to an IBOutlet in code ?

Note: If you delete a view in IB, you must first remove connections to IBOutlets.

Im having the same issue, even in code. if i press dot notation and get a red warning then click somewhere else i can no longer move back to that line with the mouse i have to press elsewhere and then use the arrow buttons to get to the error before i can fix it.