Double-check `7dav` and `prop` signals and respond

[brookslogan]

Version history for 7dav and prop signals in the API can be inaccurate. We should check that we're not using bad data here, and, if so: either derive from 1d counts, get them fixed in API & regenerate, or avoid. Unfortunately, would require updating the data set sizes and sanity-checking dependent vignette figures & statements any way.

[nmdefries]

There are/will be efforts on the engineering side to identify and (if high priority) repair data issues like this. Timeline is TBD, so we can either go ahead with this change if high priority or wait for engineering to make a decision.