Thank you, @Grzesiek2010.
I made a mistake: It is the Tecno SA6S (not SAS6).
And I should have mentioned that our data collectors' phones do not have SIM cards, so they are offline until they meet up with a supervisor and upload forms via hotspot.
I am now holding a stack of failed phones and the word 'crash' is not quite right...'hang' would be a better description. I'm not sure what happened in the moment before it entered the 'hang' state, but here is what I see:
The screen is completely black, with only the Android status bar at top. (Screenshot 1 in the dropbox linked below.)
I press the square 'overview' button at bottom left several times and the phone comes back to life...I can not proceed in the Collect App, but I can close it and start again. If I do that, and load my simple sign-in form, I can proceed as normal. If I try to 'fill blank form' and select the more complicated form, then it says 'Loading Form'. And then the screen goes BLACK again.
Note that many phones ran the complicated form over-and-over again without difficulty. The problem appeared in about 25 phones out of the 300 we had in the field yesterday.
I press the overview button several more times and get a dialog box: 'ODK Collect isn't responding: Close App or Wait'. If I wait, nothing happens. If I close App, I can go back to the loop above, but cannot proceed to fill the main 'child_vaccination_VOL_tool' form.
Some of these phones show a message on the title page saying 'system wants to do a
Google security patch and a second message about a Google Play Services 'account action required'. We've been pulling these phones back to the Ops Center, doing the updates, and when they don't ask for updates, we've been un/re-installing the Collect app and the forms. I don't have good data yet concerning whether the fixes are working. The IT guys have the impression that phones that fail and are fixed have been failing again, but we didn't start to keep careful track of this until this morning.
Because we are not crashing, per se, we are probably not sending helpful log files to Google Play. Is there a way for me to pull out a log file that might indicate why the program is 'not responding'. Why it hangs while loading the form?
Thank you again for any pointers,