I wrote about this seven months ago and the problem still persists. When using Gboard on Android to dictate a message in Hebrew, it sometimes switches to English STT. AAAGGGhhh!!
This is very frustrating, especially when having dictated out a sentence handsfree instead of typing. Proofreading the message only to find it completely wrong is a big annoyance.
Google should assume that if the non-English language is selected for a message, that setting should persist until the user has switched.