I have the same issue. Homeport on High Sierra is unusable. My friend who runs Homeport on a MacBook Air with an older OS doesn't have crashing issues. I see that the latest version of Homeport is form 2015. I wish Garmin would update it
I have had stability and speed issues before High Sierra but now Homeport is approaching complete dysfunction. I have had Garmin products since 1999 and the very reason I stay with them is Homeport. It is frustrating to have and investment in Garmin products and a software supporting them which appears to have been tossed aside by Garmin.