There are two obvious ways I can think of which we can solve this proposed contradiction. One way is to consider the context within the questions Lut(Peace be upon him)'s people answer. The second way is to consider the questions themselves.
If we look at the context of the questions (see the verses which precede the one's listed here), we notice that for similar contexts, we get the same answer. And where the context is slightly different, we get a different answer. This would mean that with respect to the same context, the answer is only one. When the question was changed (and with it the context), the answer was different, and that answer is the only answer given for that context.
The other way to solve this proposed contradiction is to entertain the possiblility that because the questions themselves differ for each of the verses, then it can be understood that for each of these questions only one answer was given for each question and so for two of the questions the answers happened to be the same.
Look at it this way: If you asked me what color is a red car and a different time you asked me what color is a red truck, because my only answer would be red for both questions, does that mean you asked the same question both times?
I think it is a bit sneaky to just compare the answers without considering the questions that were asked, and as already pointed out the context of the questions disprove any discrepency there too.
There is no contradiction here. My faith keeps growing. Islam has all the answers to any challanges. God is one.