This is a known issue (with the last update), and there is a patch in the process of being finalised for testing. The number of summons isn't the issue, but the crash is related to enemy summons (mostly with this fight).
I sent a request for access to the save.
EDIT: I emailed back a save after ending combat in the developer build of the game.
Thank you very much Raze! Tested the save and works perfectly now.
One last thing: should we expect these kind of problems in the future?
