Why has my rose totally dried out? Dry stem, leaves?

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I have a rambling rose in a large pot and one part has dried out, no browning, no pests I can see,just brittle and dry the other stalk is okay for now.
I've given it a really good water but the dry part isn't recovered,what can it be I've never seen this before without Browning etc or bugs?

I don't feed it could it be that?

The other part look fine

Is it pot bound. Rambling roses have quite large root systems.

Definitely could be but would that mean one side just dry out etc?

The only way to found out is to Take it out of the pot and have a look at the roots. If any don’t look healthy cut them out. Then repot with fresh compost.

Alternatively, If it is very large you could just cut out the brittle shoot as far as you can.

I think I will find that cut out the dried one