Mojave is a supported operating system since Illustrator version 23.×.
We request your help. Please get in touch with us at any of the other support channels – https://helpx.adobe.com/support.html . Since this is not a generic issue that we can reproduce at our end, we will need someone to look into your machine to figure out what is going on here.
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I also have the same issue with Mojave and illustrator CC. Can't open files or save them without illustrator crashing. Contacted Adobe tech support, and they stopped helping and claimed it was a Mac issue.... Uninstalled and re-installed illustrator several times, still having issues!