It might not be obvious in the photos, but in life the proportions of the bird were very ROUND, SHORT-NECKED and somewhat LARGE-HEADED, and also the jizz reminded some of the observers of a Broad-billed Sandpiper.
To me, that would rule out Western Sandpiper, which has more Dunlin-like jizz and proportions.
I didn't notice any rufous on the back and suspect it might be an artifact of the digiscoping technique (on a rather long distance).
However, it was not the best light conditions, so I cannot be sure (of the finer colour details).
To my best judgement, the initial identification is correct, although the bill seems a bit longish for the species. But it lies within the accepted variation, see e.g. this bird