Happening now since a recent update in V2019.1, possibly a little earlier
If I type a random character on the end of a line to force a syntax error to check a script is being loaded and switch to the browser and refresh there's no error.
I seem to have to move the cursor away from the line I just typed on and THEN when I refresh I get the expected error.
This is definitely not how PHPStorm was working earlier in the year and is causing wasted time when I forget that the autosave behaviour seems to have been altered or an old bug (below) has resurfaced.
There is an older bug from 4 years ago discussed here which seems pretty much identical: https://intellij-support.jetbrains.com/hc/en-us/community/posts/206704405-autosave-not-always-working-