two entries on 1861 census - why?

[topo60]

First census RG 9/3738 page 38 Framwellgate township, Ecclesiastical District St Cuthbert (Durham). (Dyke Row - bottom of the page No 212)
Thomas Bottoms Head Mar. age 23 Coal Miner, Durham Sherburn
Barbara Bottoms Wife Mar age 24 Durham Haswell (nee Hutchinson)
Robert Bottoms son age 15 Labr on Coal Mine Durham, Witton Gilbert. (Robert is actually Thomas' brother who he took in after the death of their parents, their siblings were also 'farmed' out to other relatives).

Second census RG 9/3750 page 64 Thornley Parish (Wood Street, Thornley Colliery - first names on the page No 299)
Thomas Bottoms head Mar age 22 Coal miner Durham Witton
Barbara Bottoms Wife Mar age 20 born Thornley
Robert Bottoms Brother age 14 Coal Miner Durham Witton.

I have 'proved' the 1st census to be the most acurate (from Parish Records) and Thomas & Barbara emigrated to the USA before the next census in 1871 leaving Robert (my gt gt grandfather) behind.

Why were there two entries for them and with slight differences - age, where born etc.?

[Mutley]

It does happen sometimes, often when a place of work and a home are involved.
The employer might fill in one form and the wife or family fill in another.

Soldiers can be on the list as in the barracks but the wife has put him on her form. Those working on a boat were sometimes enumerated twice. It seems people did not always end up where they were expected to be.
It is then difficult to know exactly which place they were in that night.

I notice one of the addresses is the Colliery and it has pages of miners on it, would the other be where they or other relatives lived?
If so maybe they should have been at work but were at home or visiting.