Failing postdoc?

After a successful PhD in computer science (including some awards from top conferences, internship at top industry research labs, and a good number of citations to my ~15 papers) in a top-10 US school, I got a postdoc at a top-3 US school.

I had a number of postdoc offers and chose the one whose topic more far-related to my phd thesis, in order to learn new things, get out of the box, and show that I'm not a one-trick dog (or doc? ;) ). The topic is different but not too much far away (i.e., I didn't move from theory to systems, rather from algorithms to (applied) machine learning).

I've been in my new position almost 6 months and feel like a complete failure. I can't go on with one of the projects I was assigned to and it is not for lack of trying: I just don't understand the results I'm getting because I don't know the field well enough and I can't figure out what I am actually supposed to do to improve them.

My supervisor gets quite "adversarial" when I ask for feedback and I try to explain what I don't understand. On the other hand, he says that I'm very helpful on other projects, helping the students, and a valuable addition to the group, and he would have told me if it wasn't so. Indeed I think it is true and I'm doing a good job on other projects (which are not "mine").

The project I'm failing at could have a great impact on science (not just CS) on the long term, but I feel like any engineer trained in the field could lead it to completion, so I don't find it particularly exciting. I guess I'm missing the excitement I got when I had to prove theorems during my PhD. Right now, the project involves just messy data analysis, and a lot of try-and-error coding (mostly error), all without much feedback from the supervisor (who actually told me to ask the students...which I did and they weren't exactly helpful).

Anyway, this is getting me extremely stressed (I actually started seeing a therapist about this), and I'm thinking of moving away from this position, although I may have the possibility of renewing for another year (if my supervisor would even still consider the option, which he gave me when I started)

What are the pro/cons of moving away after 1 year with not exactly much positive work done yet, especially of which I could claim ownership? I believe that right now my supervisor would not, in the future, write me a very positive recommendation letter, in my opinion.

Note that I already have offers for next year, on topics more related to what I did during my phd.