Could well be - I've seen keyboard fail completely (but not mouse) on GNOME/OpenJDK where opening a terminal and typing can sometimes unblock it, and this one where input seems to slow down, or even repeat text in odd ways.

In all cases, restarting JOSM fixes input, but then you've got to reload GPX, imagery (recent Bing capacity throttling fails), and the context.

My 8Gb RAM may need an upgrade.