There's two things which can cause that. Insufficient water in the plant which makes it lose turgidity. Think of a sausage type of balloon that becomes partly deflated, it sags. Under watering means the plant hasn't enough water to remain turgid. Over watering can result in root rot and the plant can't get sufficient water - loss of turgidity. The other thing is low light, the plant stretches to get to more light but the growth is weak and can't support it's own weight.

Thanks for the info - is it normal that only one stalk - and then all the stems off that are affected ? would you say in ghjs case it’s more likely to be a root issue ? Only i wonder if it’s a light or underwatering issue wouldn’t all the stalks be affected ? Wondering if that one root had been stuck with too much water at the bottom and is suffering because of that ? Would you suggest I take out the affected stalk? I really don’t want the rest of the plant to be I’ll too! Thanks so much again

They're vining plants so best to refer to vines rather than branches. The issue is likely the same, not enough water getting through to the vine that's wilting. Seems strange to be only affecting one. Is there a break at the bottom of it? When did the wilting start, soon after repotting or just recently? How did you repot it, replaced all the old soil or just lifted out and put new soil around the old?