App is useless on my 2020 iMac

I have a 2020 iMac, 10-core i9 Intel, Radeon Pro 5500XT, 64GB memory. Just trying to do some basic upscales and the app crashes EVERY time. It will run for about 5 minutes, then just freezes the screen for a couple of minutes, then the whole machine comes crashing down.
Anyone else with an Intel iMac having trouble?
I can run the app on my HP PC laptop, Ryzen 7 with built-in Radeon Graphics - no problem.

I have no Macs, but the general thing to try is lower the Max Memory Usage to 10%. See if it still crashes, then try and move the percentage up a little.

Thanks. Made an adjustment and will try doing a few clips.