You may sometimes feel something is off about the Japanese your foreign employees write or speak. The subject is missing, the word order is strange, or it seems to make sense but doesn't quite.
Much of that "unnaturalness" comes from translating the grammar and expressions of their native language literally into Japanese.
When Japanese expressions are translated literally into English, the meaning can change or become unintelligible. What would "otsukaresama desu" become if translated literally into English? The same thing happens in the direction from Vietnamese to Japanese.
For example, Vietnamese has the word "mệt." The dictionary meaning is "tired," but in Vietnamese, "mệt" is also used when you feel unwell. At one point, a Vietnamese employee posted "I'm tired" in English as the reason for taking a day off. When one person wrote "I'm tired," others copied and pasted it. From then on, everyone's reason for taking time off became "tired." I didn't understand what it meant, but when I learned that "mệt" also means "to fall ill," it finally made sense.
One more example. The Vietnamese word "nghỉ" means both "to take time off" and "to quit." Every time I see "nghỉ" in the company chat, my heart skips a beat for a moment: "Are they quitting?"