Motion blur fading footage?

I'm having this problem with my after effects cc 2017 where whenever I click motion blur on my clip it fades? I have no effects on the footage, I've tried reinstalling after effects and resetting system prefrences yet still the same each time? it only shows faded in the preview/project but the clips show up normal in render
(don't know if this helps but I'm currently running macOS Mojave ver 10.14.6, 1.8 GHz intel core i5, Intel HD Graphics 6000 1536 MB)
any help will be grateful 🙂
