Note, mostly for myself: This reminds me of https://bugzilla.gnome.org/show_bug.cgi?id=721761#c47 .
Could you please post a screenshot of the entire contents of your screen, or perhaps even a screencast? Details like the location of the previous/next character of whatever kind (e.g. manually drawn underline, replacement box etc.) might make a difference and might be the key to reproducing the issue. Thanks!
