Why does it sound like the t is at the end of gwisgo? There is a significant pause between "t" and "ei"
As explained in the course notes, the computer-generated voice used by Duo is pretty good but not perfect. This is one of its minor glitches.
You could try:
Going to www.ivona.com, typing the phrase into the box, then choose 'Welsh, Geraint' to speak it for you - that one sometimes avoids a glitch that Welsh, Gwyneth might be having. (Make sure that you not try and use 'English, Welsh, Geraint/Gwyneth by mistake)
Going to www.gweiadur.com (free registration) to see if the particukar word has a loudspeaker symbol next to it. If it has, click on that to hear a recording of a real person pronouncing the word