In a slide show running on WIN10 with Impress 184.108.40.206, and on the latest Raspbian with 220.127.116.11, Impress hangs (stalls). The same show seems to run continuously on Impress 18.104.22.168 (although the formatting is not quite right for the slides created with Impress 6.x.x.x).
I also created a new, simple slide show of five slides and it too hangs. The hung or stopped slide show hangs on various slides and after various times. This is happening on Win10 and Raspbian and several computers and with the show on differing media.