FWIW, I ran into this issue after updating last night and don't have the Material Theme installed or in use. S3's plugin host seemed to be directly using most of the resources.
I'm curious if everyone who has observed the issue also has SublimeLinter installed, as I suspect the issue might actually be a byproduct of how SL generates a customized copy of user color schemes. Some combination of re-setting my theme and color scheme from the SL-generated version to the original (in my case, this meant setting both from "Lyte-Dark (SL)" to "Lyte-Dark"). Just changing the theme wasn't enough to fix this for me, so it may be the case that only the scheme needs changing.
This might explain why changing away from Material Theme appeared to fix the issue for some, assuming everyone reporting this solution has SublimeLinter installed.