A group run by my advisor's former student keeps scooping my work. Is my advisor sabotaging me? I'm worried that my advisor is sabotaging me either knowingly or unknowingly. I'm entering the 5th year of my PhD in a hard science.  I had prior publications, but I have yet to publish any papers with my advisor -- because I get scooped whenever I get close to submitting one. The group that keeps scooping me is led by a professor who is an ex-student of my advisor.
For the past 3 years, my advisor has gone on sabbatical to visit with this group 2-3 times a year for anywhere between 2 weeks and 6 months. During one of his first visits, my advisor asked me if it would be okay if he presented some of my research during a group meeting. I didn't see a problem with that.  However, about a year later, this group published a paper having done basically the same experiments I had done. I was stunned and asked my advisor what was up with this. He shrugged it off and said 'this happens, we'll get you another project.'
This other group had not published anything in the area of my first project in the last decade.  I figured really bad luck.
Fast forward another year.  I've started a new project in a different area of my field.  My advisor again asks if he can share my new research with this group. I said I didn't want to share it this time.  I thought this was very understandable given what had already happened, but my advisor got upset at being told 'no.'
At the time my advisor was visiting them, I was struggling to justify why I was getting a low value for a value I was trying to determine experimentally. Some time after my advisor returned home, I realized I had made a mistake in my analysis which, after correction, put the value where it should be.
Several months after my advisor's visit, the group came out with a paper on exactly what I was working on. Bizarrely, the paper they published included the low value / result that I initially got before realizing my mistake, they offered very little explanation for this low value. Their own theoretical calculations suggested it should be higher.  But it's the number I had when my advisor visited them.
This other group had never before published anything in the area of my second project. When this professor was a student with my advisor they worked on a different area of my field than I am working on now.
It feels like my advisor is trying to get me scooped, or doesn't know any better. My advisor visits so often it seems unlikely he isn't aware this group is working on what I'm working on. If that's the case, shouldn't he warn me? How do I proceed with future projects / my advisor?
My advisor also has tried to abandon each project after I get scooped, but that doesn't make sense to me, either. The other group only does a single experimental run, while I do several. I also think they've made significant mistakes, which my work can correct. I think my work still merits publication.  Any advice on how to handle this situation would be much appreciated.
Something is clearly wrong here. If your supervisor is not alarmed, talk to another senior person and make pretty damn sure your supervisor is correct not to be alarmed. There are many people you can ask: your thesis committee, your head of department, a trusted faculty member, someone from the School of Graduate Studies, and so on.
Ask to speak in confidence - something is clearly wrong, and that something could be your supervisor.