Run your Gigapixel to get the new update. I have only tried it on one picture but it seems even faster now. The "clear all" has been moved to the upper left corner and the interface is refreshed. The new version is 3.0.3 and one nice feature is after loading a picture to be resized, you will see the exact size of the finished version.
1-25 added edit: I'm using a Windows 10 (ver 1809) AMD 2600X cpu tower computer with a Radeon RX580 graphics card. The new version of Gigapixel works fine for me and I suspect for most Windows users. The problems below mostly seem to be with Macs. This version remembers the suffix you assign which is something I requested in a post.