Thank you pixie and stachi for you messages. I agree with you and will go for this "mini postdoc". For me, I don't think there is any problem if one stayed in the same place. If he is productive then I don't see any problem. However, the general consent in academia that this is not a good indication.

Hi Satchi,
Well it is mentioned that working at the same institution and lab would give an impression that you are stagnant and not willing to learn new techniques. I do not agree with this but this is generally the impression in academia.

Hi All,
I have an opportunity to work for 3 months in the same lab of my PhD. I learned that, generally, this is not a good idea. However, I will be working in a joint project with one of the top 20 universities. The lab in the other university is number 1 in the field and the research is slightly related to me PhD thesis. I consider it a good opportunity to work with this team, but at the same time heard that working as a postdoc in the same institution can harm more than benefit.
Due to visa issues it is almost impossible for me to go to the other top university so we ( me my PhD supervisor and the other lab) to work in my PhD supervisor lab in a joint project. So it is a matter of practical difficulty rather than an academic barrier.

What do you think? Should I go for this opportunity or not?