@SBisson @Catrope @kostajh -- after @nettrom_WMF's analysis from T206380#5045440, we see that the group receiving Variation A in Vietnamese Wikipedia has a higher abandonment rate than those in the control group. This is only occurring in desktop. Mobile shows no differences.
Though we don't know exactly why this is happening, we want to turn off the survey in Vietnamese in case it is turning away good new editors. We will continue to investigate and potentially turn the survey back on later.