Thank you for the input!
In fact, I was aware of Path Randomization after reading a documentation on the website. And I did move ImageJ.app out of the ImageJ folder to Desktop, and copied it back to the ImageJ folder before.
I've just double-checked the path in the Image>Show Info window, and interestingly, the "ImageJ home" path still starts with "/private". So I just tried again moving ImageJ.app out of the ImageJ folder to desktop, and then copying it back to its original folder. Unfortunately, it still doesn't work for me although I tried this numerous time.
I think, this might be unrelated to this issue but I cannot move files out of a folder in /Applications by holding down "alt" key, but "command" key worked for moving files, which is interesting to me as well...
Do you have any other suggestion to fix this issue?