There are many reasons why this may happen. In light of this, let me give you a few possibilities.
The most important reason for different scientists giving different answers to the same problem is as Lesley Blair Ph.D. of Oregon State University explains:
[S]cientists differ in their knowledge, beliefs, and abilities. As a result, different scientists can analyze similar data in different ways and ask very different questions.
The two main reasons, then, are (1) taking different approaches to analysis of data and (2) asking different questions about the same data.
Another reason might be that not all experiments or problems are the same even though they seem the same. They might look identical, but there might be a few unaccounted variables. These variables can cause there to be different answers.
Also the place where the experiment takes place also matters. Not all contexts or surroundings are the same. For this reason, geographic or atmospheric differences or anything other context may cause variation.
In addition there might be pure and simple error on the part of the scientist. Scientist are fallible, even though they take great precautions to be precise.
Another reason is also the importance of selectivity. If a company pays for the experiment, and they favor a certain outcome, while there is another company, and they favor a different outcome, you might have two different outcomes. Selectivity always plays a role.
Finally, there might also be fudging of data. We cannot leave out this possibility. Scientists have at times proven to be liars as well.