LinkLayer

I have also been noticing the Inpainting tool is laggy, and it seems like it used to always be fast.
Affinity Photo 1.7.3
Mac mini (2018
3.2 GHz Intel Core i7
16 GB RAM
Intel UHD Graphics 630 1536 MB
I have usually been editing TIFF files, fairly simple stuff, with one or two layers. Max of ~ 13 MB file size, Max of 4 images open at once.
 

I bought Affinity Photo on the Mac App Store.
I'm happy that you were able to reproduce this.  That way I don't look like a crazy guy. When I found this problem, I think it was only about the second time I had ever used the batch file feature. I'm surprised if I am the first to report this problem.
This is not impacting my work or anything. It'll probably be fixed before I need to use it again.
I'm happy with the speed! The batch processing runs plenty fast, even on my older Mac.  What's not so fast is adding files to the list to be processed. That takes much longer than to actually process them.
Thanks!