I am unable to reproduce this with Jaws 2018 latest release and Version 65.0.3292.0 (Official Build) canary (64-bit)

I can reproduce locally - all versions of JAWS, all versions of Chrome. Pressing Enter in the Compose field of Gmail switches out of forms mode. I was able to bisect it to this change that Aaron made 5 months ago:

https://codereview.chromium.org/2931893002/ (More precise use of multiline state)

I'm guessing Gmail maybe made a change to their contenteditable, maybe the role or aria-multiline or something like that?

I don't think the statement about Firefox is true. The bug also occurs in Firefox.

Firefox 52.5.2 (64bit) ESR
Windows 10 Enterprise Version 1607 Build 14393.1770
NVDA 2017.4
JAWS 2018.1712.10 Private Beta 

Here is what I see in Firefox when I take a closer look. The problem appears to be intermittent to me since I get different results upon repeating the same actions. Perhaps I am missing something subtle here? 

# Launch Firefox ESR and JAWS 
# Launch non-corp GMail, compose new message
# Start typing, press enter

Trial one: 
Expected: newline inserted, forms mode is still enabled
Actual: forms mode is exited 
If you continue to type anything but an enter character, you are moved out of focus on the text box. 
If you press enter again, place is held, forms mode reentered and you can keep typing at that point. 

Trial 2:
# Close out JAWS, reopen 
# Launch non-corp GMail, compose new message
# Start typing, press enter
Works as expected. Enter key will not take me out of forms mode, just enters a newline character. 

Trial 3:
Works as expected
Trial 4: 
Works as expected
Trail 5:
Works as expected

This means that if I close and open JAWS/Chrome 5 times in a row, the bug replicates just once. 

Thanks,

Laura 

This will be fixed by the Gmail team by adding aria-multiline to the their compose field.

Gmail team has fixed this bug and it will go to production soon.