It’s hard to tell from the photo- but if the roots look grey and mushy, not white and are just falling off then you have root rot. If it progresses the stem will start to get soft. I don’t know how effective this is, but i have read several articles that suggest watering once with am 3% hydrogen peroxide will help treat root rot. Also remove any mushy/dead roots before repotting.

If it’s not root rot there are several other things that cause shallow/weak roots. Improper watering being a very common one. Hope that helps!

Nora,
Thank you for replying.
Good news is, it isn’t a root rot so I’m relieved! The stems are healthy and firm, not mushy at all. So there’s nothing to worry I suppose.
The plant is healthy as of now, touchwood!
Thank you (:
Queen

Well, not so fast pls. Sorry but I doubt that soil is good for succulents, it's too finely particled. The pebbles are good but the fine stuff is likely to get stuck in the roots (like your residual older soil).

If I thought you were in the US, I'd suggest you use C & S mix w/ Perlite (50/50 each). But am guessing you're in Europe, so don't know what that's called in various places there.

Karen,
I live in India. I tried looking for cactus & succulent mix, but nobody seems to understand what that means, atleast around my place!
So I have ordered the C & S mix online, along with Perlite. Once they arrive, I shall mix them in 50:50 ratio as you and others have mentioned earlier.
Thank you (:
Queen