FancyZones on custom monitor layout is vertically squished upwards when editing

[framlingham]

Microsoft PowerToys version

0.65.0

Installation method

PowerToys auto-update

Running as admin

No

Area(s) with issue?

FancyZones Editor

Steps to reproduce

I have three monitors laid out like this:

When I go to edit a layout (since adding monitor 1), the layout grid doesn't extend all the way to the bottom of monitor 1. And the position of all flat splitters are a bit off (vertical splitters seem positioned fine).
This is what the zones draw as for my layout named "||=||". You can see that I was trying to get a few splitters to align with the top of the central monitor/screen, and had to add new ones because I couldn't grab them once I dropped one too high (by moving mouse up on monitor 1 ;-)).

This is what the zones look like in use with various windows Shift-dragged into the zones as annotated:

This is what it looks like when editing the splitters:

I hope this is enough info!

PowerToysReport_2023-01-04-15-29-37.zip

✔️ Expected Behavior

The layout editing and actual locations on screen to agree.

❌ Actual Behavior

The layout while editing is vertically squished to occupy the top (approx) 80% of the virtual screen extent, but in use, there is no vertical squishing. I can't position flat splitters properly because of the 'squishing' while editing.

Other Software

I can't think of any software that would be interfering with this

Edit: to update annotated screen grab to show full extent

[framlingham]

(I think maybe the new monitor is #1 because I have it set up for USB touch input. It's a https://www.ebay.com.au/itm/393064445491)