Earlier this year, I interviewed and received offers for two postdoc positions from competing universities, with one- and three-year contracts, respectively. The first is more related to my PhD, while the second is a bit distant but still in the general area of my discipline. I eventually accepted the second one for different reasons:

1. It's in a multidisciplinary research centre, and the description was that I will be part of a large team working on a massive project, which I found really exciting and non-traditional.
2. Huge amount of money is being poured into this centre by the government, so there's a good potential to grow.
3. The project itself is interesting and I will gain different skills by pursuing it. The intended work was of industry-like nature
4. The PI was extremely keen to have me onboard, which made me feel valued.

On the flip side, the university is large, but I will be working at a small campus. Most of the team are from one discipline and only a couple of members are actually from my discipline (say, for example, most of them are mechanical engineers, but I'm an electronic engineer). The PI is not from my discipline. 

The disadvantages did not mean much to me when I received their offer as I considered myself joining an industry R&D department, which I also confirmed during the interview, and from the position description.

Once I accepted the offer and joined the research centre, I was shocked that I was assigned a very boring project that I will work on alone and doesn't fit my background. It's academic in nature, but with almost zero supervision. The potential to publish in reputable venues is small. I also found out that they hired another postdoc to fill the advertised position. This was a dead-end for me. I felt like I was put under a glass ceiling not to join the other university (a competitor). I deeply regretted accepting this offer, but at the same time, I cannot resign as I have just moved to a new city with a spouse and kids. 

The good news is that I did a really great PhD on a hot topic, and was approached by 3 universities abroad to co-supervise PhD students distantly. 

I communicated with my supervisor in this regards and expressed my feeling of being alienated and my preference to be integrated with the large team and be given a role as discussed during the interview. He agreed and gave me a task to do, but never replied to any email I sent later. He ignored me big time. Under the fear of being kicked out and putting myself and family in a financial hardship, 6 weeks later, I agreed to work on the project he assigned me earlier while working distantly with the other universities to keep my passion and academic career going. Ever since, our communication improved but still I feel isolated and doing worthless work.

What's your advice for me? Finding another job is a top priority for me but that is going to be hard due to job market trends and the limitation of moving with my family to a new city/country for another time (kids, school, etc). I have been in this position for 4 months - long enough to hate it.