Google Voice typing no longer works in French, works in English Problem: voice typing broken

On a Samsung Galaxy S5 with latest OS (Android 6.0.1) setup to French language, Google Voice Typing worked great. I need it regularly in French (and sometimes in English).

A few weeks ago, it suddenly stopped working. It would write "Appuyez pour parler" and immediately "Reessayez" without any listening time.  English for that: "Tap to speak" and "Try again".  Connected via mobile or wifi or not at all does not change anything.

Note that the microphone icon in browser and Google search app still worked and recognized French. What fails (and what I need) is the microphone option built with the virtual keyboard.

Searched and tried before asking: voice typing broken, in French only

No real hint on the web or even a trace of someone having same problem (language-dependent brokenness).

I suspected conflict with some app, so uninstalled some apps. No benefit.

I changed global (Android-level) UI language to English (to see official labels for this question) and voice typing worked again... in English.

I changed global (Android-level) UI language back to French and voice typing failed again.

While keeping French UI, I set up English as primary language for voice typing, keeping French as additional, and it worked, in English, inventing English sentences if I spoke French.  As soon as French is primary language, voice typing fails again.


Can someone explain what happened?  
How to get French voice typing working again?
I noticed that Android had locally an offline recognition pack for English.  So, I ended up selecting the French language for offline recognition, Android downloaded a pack and now it works.  

Not the actual fix to the initial problem.  It worked online before, but in practice it works.

It does not explain why on-line speech recognition would fail.

Also, is offline recognition as good as online ?

Edit: in order to reproduce the problem with logcat to get a log, I uninstalled offline French pack and now voice typing works at all times, even after rebooting.  So, the problem looks like it's definitely gone and we'll never know?