The same Geotiff is rendered differently if JAI-Ext is enabled or not.
I originally found this in 2.15.x and confirmed it exists on 2.14.1 too.
Download the latest 2.16.x platform independent binary
Publish the attached float32_nodata.tif file as a simple GeoTiff
Use the default "raster" style without any change
Preview it (see the attached it.geosolutions-float32_nodata_bgcolor_JAIEXT.jpg)
Note: I used the BGCOLOR parameter to see the data boundaries
Restart GeoServer with the "-Dorg.geotools.coverage.jaiext.enabled=false" parameter to disable JAIEXT
Preview the layer again (see the attached it.geosolutions-float32_nodata_bgcolor_NO_JAIEXT.jpg)
See the attached "screenshot - annotated.PNG" file to see how the file looks like in QGIS.
I used the purple background color to see the difference between the nodata area an the maximum value area.
The images are different:
With JAI-Ext the full extent is black
Without JAI-Ext the nodata is black and the rest is white
The sample file has the following content :
Total pixel count: 100
NODATA pixel count: 25
Value Pixel count
Tested on Linux with OpenJDK 64-Bit 1.8.0_181 and Window 10 with Java HotSpot(TM) 64-Bit 1.8.0_161