I have had this issue in my Citigo too after around 4 years, and I have read about it being quite common (also in VW Up's and Seat Mii's)
I would not remove the heatshield, but I would also not replace it for a new one, as that is quite a lot of work and I'd expect a new one to fail again in the same way.
The heat shield seems to be quite thin aluminium, and due to corrosion and vibration it eventually breaks around the washer/clip that holds it.
What I ended up doing, which has held so far for more than 5 years surprisingly well, was to improvise my own aluminium washers, from the bottom of aluminium cans (any beer or soda can).
The bottom of the can is quite much wider than the original washer, and has a nice dome shape, which fits nicely, specially in the front of the heatshield.
Note that I reused the plastic spacer between the new "aluminium washer" and the metal clip, to prevent the metal clip from touching directly the aluminium. The "aluminium washer" does touch directly the heatshield.
I had tried first with a bigger steel washer but that only held for less than a year. I think the problem is that the steel corrodes the aluminium very fast, and due to vibration cuts thru the heatshield in its edges.
I just added today another 2 of these "washers" in another 2 of the original clips which broke recently. Now only 1 out of the 6 supports is holding on the original heatshield and 5 are helped with these aluminium can bottoms.
The exact way I did the washer out of the can was to cut it with a bit off the can bottom ridge, bend the ridge a bit inwards so the rim of the washer was a bit "reinforced", bored a 4mm hole in the centre for the car body stud, and did two perpendicular cuts centred in the hole (so there is 4 flaps that can catch in the stud a bit on their own).
Note that even though this new washer holds a bit on its own, I still used the VW clip to hold it in place, as I'd expect it to otherwise corrode around the stud and fall off quite fast.
You can see here 2 photos, one of a fully newly installed one
and another of one that has been holding there for ~5 years:
(The brown color in the car body and heat-shield is just an extra anti-corrosion sprayed coat)