The simplest solution to me seems to just speak with them, vocalize your doubts. In short - be honest with them and with yourself - you're after getting some re

The simplest solution to me seems to just speak with them, vocalize your doubts. In short - be honest with them and with yourself - you're after getting some responses. If they will try to not answering - you immediately know it's a red flag. If they give you explanation - just do the research if their explanation makes sense.