Hi clementijeff. I have a similar system to yours:
27" iMac 2.7ghz i5, 24 gig ram, El Capitan 10.11.6, and running S1 3.2.3.
Ever since updating OS X to 10.11.4, then 10.11.5, and now 10.11.6, S1 has been getting increasingly unstable. The most stable system I had was on Yosemite 10.10.5 which I still have on a second partition on my imac hard drive. I just booted into it tonight having got fed up with yet another crash. On this partition, I am running S1 3.1.1, but I will upgrade to the latest tonight and see what happens.
Most of my recent crashes seem to involve BFD3 (latest build), but not all of them. Are you running BFD3?
I think I am noticing that most crashes seem to be grahpics related, but I'm dont fullly confident of that. If BFD3 crashes S1 it always seems to happen when I click on some part of BFD3's graphic images of say kit pieces, or presets, etc. I have had similar crashes with a couple of other plugins, including MT Power Drumkit. However, it gets confusing when I also get crashes that dont involve any third party plugins at all.
I just found this thread on this site, which may help you: I will try it myself tomorrow sometime, but for now I just want to make sure Yosemite is still stable.
http://answers.presonus.com/5057/running-professional-capitan-studio-quitting-unexpectedly
I will bookmark this thread.
Good luck.
Gary.
