Issues with maximizing windows

Hi, I’m using version 1.51n on Xubuntu 16.04 with two monitors. I am experiencing some problems when trying to maximize windows. The images I’m looking at are usually larger than my monitors, so when I open one, it is shown at 50% size by IJ, in a non-maximized window. In general I want the image to take up as much display room as possible, but when I try and click the ‘maximize’ symbol, nothing happens. What I need to do is zoom the image to a size that is larger than the display, then I can maximize the window it is shown in, and then I need to scale it back in size with the mouse wheel until it fills the display.
Then these steps only work for the main display–on the second one, I can’t maximize ImageJ windows at all! I need to use the cursor there. When zooming out, the window will shrink to the image size, but it won’t expand again when zooming back in. Of course this is pretty annoying… so is this normal ImageJ behaviour or is my OS to blame? Is there a workaround (e.g. force all windows to open in fullscreen or something like that)?

I’m having a similar issue on a brand new Windows laptop. When I click maximize, it does not fill the whole screen, nor does the window think that it’s maximized (maximize icon still there). I can manually stretch the borders to fit the screen. Zooming in and out with the mouse wheel causes the window to unexpectedly change size, although I think it stabilizes at some point. I’m using a single monitor connected to my laptop as my main display (laptop screen is off) at 1920x1080 resolution.

The original issue I had has been resolved by, I think, switching to Ubuntu 18.04.