NBC/Marist NC: Biden +6

[TiltsAreUnderrated]

Changes among registered voters (with July 14-22):

Biden 51% (n/c)
Trump 46% (+2)
Other 2% (n/c)
Undecided 1% (-3)

[TiltsAreUnderrated]

Fuller release: https://www.documentcloud.org/documents/7279122-Xyz-NBCNews-Marist-Poll-NC-Annotated.html

1049 registered voters, MoE: 4.1%
800 likely voters, MoE: 4.7%

Also among likely voters:

Other 2%
Undecided 1%

[TiltsAreUnderrated]

Marist is usually a good pollster, no?

Ask Sen. Donnelly and Sen. McCaskill.

Marist's final polls had McCaskill at 47% (she got 46%) and Donnelly at 45% (he got 45%).

No.  they had Mccaskill at 50 and Donnelly at 48.

They most certainly did not:

Indiana they had Donnelly 45, Braun 42, Brenton 7, Other 1, Undecided 5
Missouri they had McCaskill 47, Hawley 44, Campbell 3, Crain 2, Other 1, Undecided 3

Republicans in both appeared to benefit from third parties underperforming their polling (as they almost always do) and winning over most undecideds (common in safe states for the dominant party).

You are both right - they had two variants for the final poll, ones with named third parties and ones without. Among likely voters, the ones with named third parties had the results you've posted and the others had McCaskill 50, Hawley 47, "Other" <1 and Donnelly 48, Braun 46, "Other" 2.