Point jumps to end of buffer

[contrapunctus-1]

Firefox v69.0.2, 32 bit. GNU Emacs 26.1 (build 2, i686-pc-linux-gnu, GTK+ Version 3.24.5) of 2019-09-23, modified by Debian. atomic-chrome v20180617.724 from MELPA.

1. In the browser, click the GhostText button, select a field.
2. Switch to Emacs, move point to somewhere other than the end of the buffer
3. Switch to the browser (the same tab must be open; switching to another tab, or to applications other than the browser, will not cause this).
4. Switch back to Emacs. The point has jumped to the end of the buffer.

I can replicate it with emacs -q