We've just released Xenonauts V1.59 for PC and Linux, and will be releasing the Mac version shortly if no bugs appear in the next 24-48 hours.
V1.59 is the revised version of V1.58, which we rolled back a week or so ago because we were concerned about stability issues. V1.58 included several fixes over V1.56, the biggest of which was a fix for an annoying AI hang.
Thanks for your patience!