No, it is extremely unlikely that this happens. Please email us more details about FileManager's version number and build number. You can find the version number and build number from the About dialog.
Please also email us an example image. FileManager doesn't attempt to change your orignal image at all. The compression and de-compression happen during transfer only. When it is uploaded / downloaded, it is not changed at all.
DriveHQ creates image thumbnail and preview-size image when an image file is uploaded. In certain cases, the preview image can be larger than your source image if the source image is very small.