The easiest way to reproduce the problem I'm having is to do the following:
1. Open Photoshop and create a 1000px x 1000px document @ 300dpi 2. Right-click on Layer 1 and choose "Artboard from Layers..." in the dropdown menu. 3. In the "New Artboard from Layers" dialog, change the width and height to both be 1000px and click OK. 4. Make sure you have the Artboard tool chosen and grab a corner to resize up to 4000px wide, making sure to hold SHIFT to constrain the resize.
Expected behavior: Newly resized artboard would be 4000x4000 in size.
Actual behavior: Artboard is no longer a square shape- the height dimension is now off a (seemingly) arbitrary amount.
Stray observations: - I can do this with 2 documents side by side and the amount the height will be off between the 2 documents is not consistent. (can be higher OR lower!) - The error seems to compound over time if I repeat the resize process- especially if I resize up, then down. - The error seems to get larger if I resize to a very large number (e.g. 10000x10000) - The error that gets introduced appears to be worse if my initial crop is not a square (e.g. start with 2183x987 and constrained scale from there). It's just more difficult to see the error as you have to crunch some numbers to find out what the height number should be.
Details: - I am using Photoshop CC, v19.1.5 on a Mac, running High Sierra, v10.13.4
That said... This is behavior I've been experiencing for at least a year across multiple versions of both Photoshop and MacOS...