If you don't want to dig deeper, it is applicable.
Just for clarification: when you open an image with Bio-Formats in the Hyperstack Viewer, close said image again, and click the status bar, the Memory Monitor does not show a decrease in memory? Or are we talking about automated Garbage Collection once an image is close, i.e. without clicking the status bar?
I cannot reproduce the issue on Ubuntu 16.04.1, Java 1.8.0_66, Bio-Formats 5.5.0. Closed images get properly flushed when a Hyperstack Viewer is closed and garbage collected both automatically (when e.g. a new file is loaded and the maximum heap size is approached) and manually.
Any news on the macOS front, @dgault?