I have to reauthorize my license every time I run it on one or the other
Since you are using a trial license, you can only run PixInsight on a single machine and platform at a given time. This is by design. See FAQ 2.19:
http://pixinsight.com/faq/As noted in FAQ 2.19, this restriction does not apply to commercial licenses. See FAQs 2.5 and 2.6. See also FAQ 2.10 for the procedure to move your trial license to a new machine. Alternatively, you can request a new trial license with a different email address (for security reasons, our system does not allow two or more licenses associated with the same email account).
"Could not duplicate bug closed" Honestly I'm surprised by your tone towards customers in this, and other threads I have read here.
That's just how software development and bug fixes work. To solve a nontrivial problem, I need to understand it first. Normally, to understand a problem and find a suitable solution, I need to reproduce it on at least one of my working and testing machines. This is not the case in your bug report: I cannot reproduce a similar behavior on any machine and operating system. I have several machines running up-to-date installations of OS X 10.10 and 10.11, and PixInsight works very well on all of them.
Instead of providing useful information to help me understand why the problem happens, you said "for the price it really shouldn't be this buggy and unstable". That's not very nice of you. I work hard on PixInsight to build a powerful and solid image processing platform. If you think that the price is high, there are much cheaper solutions in the market, including many gratis products. Honestly, the price of a PixInsight license is quite low in my opinion, considering the capabilities of the software and the way we give our users freedom to install and use it on unlimited machines and four operating systems, with unlimited updates.
I understand your frustration. However, please understand also my frustration each time I receive a complaint because of a problem that I am unable to solve since I cannot reproduce it. In most cases these issues are caused by elements external to PixInsight. This includes misbehaving third party software such as drivers, utilities, wrong system updates and malwares, as well as failing hardware. In other instances there are problems caused by our supporting software tools, including compiler bugs and bugs in third party libraries, although in the latter case the issues are usually easily reproducible. The world of software development is hard for a complex multiplatform application; there are simply too many things that can interact badly, in surprisingly weird and unexpected ways.
The only thing I can do is to release a new version, hopefully better and more stable. I am doing the same since 2004, when I released the first version of PixInsight LE. The next version 1.8.5 will hopefully be released somewhere before Christmas. It will use at least Qt 5.7.0 (version 1.8.4 uses Qt 5.5.1) and much evolved versions of our own development libraries.