Affinity Photo Mac freezes when using flood select

[Samweow]

On this one .afphoto file, whenever I try to use the flood select tool, affinity photo freezes and I must force quit it by pressing control-alt-escape followed by force quit with affinity selected(which says not responding). The problem isn't repeated on jpg files

This is the .afphoto file.
https://drive.google.com/file/d/1DmJd25IhB8akohlENhKAwXwBKSmgwVcr/view?usp=sharing
I also attached a photo which shows the spot I'm trying to flood select

I am running AP 1.8.2 on Catalina 10.15.2 on a 2013 Macbook Air
I can send any crash reports if you tell me exactly what to send

Edited June 7, 2020 by Samweow

[Lee D]

The overall size of the canvas 4272 x 15000px (60" x 205"/5ft x 17ft) may be having an effect on the flood tool process. On my 2015 iMac running Affinity Photo 1.8.3 on Catalina the app will not respond for about a minute, then the selection is made, so it is making the selection during this process.

Even though the layers are pixel based, If you Rasterise the layer you are wanting to select from this does speed the process up for myself.