I found this thread:
Which is exactly what's happening to me, however I see that it's listed as closed and fixed in version 3.4.1 b858, but I'm on 3.5 build 875 and still seeing it. My config:
MacBookPro11,4 (15" Retina - Mid 2015)
16 GB RAM
High Sierra 10.13 (17A405)
Alfred 3.5 build 875
Just wanted to let you know that it's still happening. Switching to Alfred Mac OSX theme did resolve the issue, but Frosty Teal (which I was using) is very slow.
Cheers,
Emery