I have used PE14 for many years and have had very few problems which I have not been able to resolve. Now I have upgraded y Mac mini to High Sierra O/S and am having serious problems with two features of the program which I use frequently. When trying to preview a video clip the program will freeze and a restart of PE14 is required often loosing unsaved changes. Similarly with the zoom tool. If I try and perform a zoom into a still picture clip all is well until I try to save the effect with the Done command. Same result as with the clip previewer - lost changes and time wasted. I have tried numerous reinstalls with the same result. I, and many other PE users, need this problem sorted out urgently.
I use High Sierra O/S 10.13.4 on my iMac with 2.11TB hard drive and 8GB of memory. How much memory is available in your Mac mini? Zoom can gobble up memory, and if all other aspects of your editing with your Mini work, that may be the problem. How does it perform using plain vanilla video editing and rendering?
My Mac mini is a 1Tb machine with 16Gb of Ram so should be able to do the job. I have used PE14 since its release and updates have been applied when available. The problem with the zoom into still pictures and also the freeze that occurs when a video clip preview is opened has only happened since I updated my O/S to High Sierra. Normal video editing and rendering show no problems at all.