The aerial part is very delicate. Mine too was half damaged but luckily it resprouted immediately below the damage and now it does roughly 3-5cm per day.
Maybe it doesn't like the substrate or you are watering too much?
Since it's so delicate I guess it doesn't stand wind well too, are you keeping it outdoor with windy days?
I am keeping mine inside in a well lit position until it's large enough.
If it resprouts so readily, I don't think I'll have to take drastic measures. Thanks!
It's usually not too dry, nor too wet; I'd say it's well balanced (but not today, I just watered right now 'cause it was looking dry). The substrate in this tote is mostly compost, so I doubt that's the issue. It's outdoors, but in an area that's well protected from the wind, and with only some morning sun (indirect, because I've placed the vine amongst other plants for protection). I think it's mostly the shipping stress that's causing this.
Only 1st year bulbil-grown plants are so thin at the start, and even then if sprouted in-situ (as opposed to protected) they can handle tough conditions and moderate wind fairly well. Vines grown from tuber cuttings start off much stouter and stronger. I have a Florido alata sprouting right next door from a tuber cutting, and the difference is rather big.
Here's a picture of the upper vine, the tip damage , and the Florido yam (to the right of the picture, with tomato leaf and stem in the fore and background respectively, and the Ube vine just behind the Florido sprout):