Windows 10 Pro Build 1803 17134.5
(Release Preview Insider)
Attempted to Install Avast, Well Behavior shield keeps shutting off, will not stay on, Antimalware executable for Defender using 65.7mb of ram just with a little bit I have open, Any idea when Avast gonna fix this issue? Releases Monday for everyone for early adopters via ISO/Media Creation Tool
It better be fixed by 4/30/2018 when the official release happens. 
Seems to be fixed at this point, Installed 17134.1 From Media Creation tool ISO, Another Machine installed from that to, Upgrade in place, and older AMD FX Desktop Clean installed, and Avast reinstalled on that one (machine that had the problem) All appears to be working fine with Avast now, So Maybe was an error with the OS itself/Preview build
https://forum.avast.com/index.php?topic=156141.msg1459636#msg1459636
No problem here with the latest upgrade of Windows 10 and Avast.