This is normal for an NABG (non-anti-blooming gate = it blooms or overshoots when overexposed) camera, as it does not have anti-blooming technology.
A science based telescope may have this kind of camera because as It is actually a *better* camera than many anti-blooming cameras due to its high quantum efficiency, and its deeper full well depth.
That means that something you'd have needed to expose for 5 minutes on an STL-11000, you can exposure for only 3 minutes here. The full well depth was chosen to allow research use to get more accurate readings on longer exposures, as researchers don't care if a bright star blooms -- they only care about their target object, usually much fainter.
Blooms are easily removed by your stacking program (but you *must* do it as the very first step after calibration -- don't stack, don't register or align), or by taking additional, shorter exposures of the region and using HDR blending techniques to combine disparate regions of exposures of different duration. To remove existing blooms via software, I prefer CCD Stack from CCDWARE.COM, though MaxIM DL (cyanogen.com) has a decent bloom removal tool as well.
The CCD details are noted in each telescope's info page.Another option you should try asking other members about removing such artifacts on our Members Facebook Page or try sites such as the Iceinspace astronomy forums.