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This was what worked for me. Have posted the issue on Malwarebytes' user forum. Apparently it had happened before with a previous Affinity Photo download which has since been whitelisted. I requested the same green light be afforded AF 1.8.2

Have repeatedly attempted to download 1.8.2 but have been prevented by Malwarebytes' Website blocking of it due to a suspicious download. How else might I be able to successfully update Affinity Photo in Windows 10 Pro Version 1903, Build 18362.592, Intel Core i5-6500T CPU @2.50GHz, 16GB DDR4, Intel HD Graphics 530?

If you've been experiencing similar issues with a system which by comparison is a Lamborghini next to my Chevy Volt, then I don't feel so badly. Still, it stinks to have to put up with the constant stalling when in certain modes. And perhaps I'd be of a similar indifferent opinion if it wasn't happening to me; lesson taken and learned regarding support. Thanks again, verysame.

As you mentioned, the noise of the fan is the prime indicator that something is huffing and puffing, which typically goes hand in hand with the CPU revving up. I had previously neglected to reference this additional symptom, though the two (high CPU usage and runaway fans) historically go hand in hand. I'm aware that my system is a bit long in the tooth (6th gen i5, Intel "HD" 530 graphics); Luminar 4 takes an inordinately long time to both load and process images, which is a reason why I began to use AP more and more. I suspect as you do that there's a strong possibility that another process is a contributing factor. In the meantime, users with semi-antiquated rigs like mine will have to endure and suck it up.

My apologies for not taking particular note of what Dan C previously posted regarding AP's using all available CPU resources. I'd read of other users complaining about the same high CPU issue but suspected it was either my older Intel graphics or a glitch in the program's ability to play nicely with my system. If AP is designed to fire on all cylinders for certain commands then I guess it's a fact of life I'll have to deal with. Thanks.

Thanks for pointing out a setting that I was up to now unaware of, Greyfox. On checking with my installed Affinity Photo it appears that the settings on mine are identical, or at default levels. In this particular setting I don't however see any setting for CPU usage, which was the main reason for my post. It's the surge of CPU when using Denoise Live Filter Layer that sets the fans in my desktop to run louder and more noticeably. Is performance like this merely to be endured while using Denoise Live Filter, or is there a more hidden setting that can be tweaked to mitigate the higher CPU usage?

Apologies for the intrusion, but I've been dealing with exorbitantly high CPU spikes in Affinity Photo 1.73.481 with .jpeg (not RAW) files when using Denoise Live Filter Layer. System specs are: Microsoft Windows 10 Pro, 64 bit, 16GB DDR4, 2.50GHz Intel i5-6500T, Intel HD Graphics 530. I'd like to know what might there be that I can do about this issue. I'm also curious as to how/where to locate Affinity Photo Preferences>Performance so as to procure a screenshot.

Well, the mystery of its arrival/installation persists but is fading fast in the rearview. Despite the fact that I can't recall precisely how Affinity Photo 1.5.1 wound up on my MBPr, it's definitely not a trial version. Thanks for the reply, though. Will continue to try and get both accustomed and familiar with it.

Purchased Affinity Photo on MAS, at a very attractive price, I might add. Installed same and am learning to use it on my new rMBP. It opens fine in version 1.5.1. Have downloaded a ton of tutorial videos. Thanks a LOT for those! Really. It's almost unheard of in this day and age to even consider that there could be such a treasure trove of helpful video tutorials so readily available to both users and prospective or inquisitive ones. The problem, if it even IS one, and one that I suspect would vex anyone at Affinity/Serif, is that the visible Affinity details in the Purchased section of my signed-on Mac App Store account page reads “Download” and not “Open”. Now, a reason for this could be that at the time of purchase (at that very attractive price) I was currently running with Mavericks (OS X 10.9) in a mid-2010 MBP, and with Affinity requirements being at least Yosemite (or was it El Capitan? can't remember), I didn't attempt to install it. But once paid for, any app can be re-downloaded/installed, correct? Well, even though it hasn't been a long period of time since AF has lived in my Applications folder I can't for the life of me be absolutely certain that it got installed on my rMBP via the Mac App Store, and I sure as heck don't want to risk any unforeseen event as the result of re-re-installing it from MAS merely for the sake of it. Does any of this sound familiar to anyone? Had a similar experience? I'm all ears.