In certain cases (maybe with 70 images?), the grid produces by running juxta with default values results in an image grid which is very narrow (2 images is observed) horizontally and consequently very tall vertically (oberserved 35 images).
The problem was caused by RAW_IMAGE_COLS being auto-guessed in one call to juxta.sh, then exported and used as-if by subsequent calls. Closed by 3f79d3ae300f9cdf0724cd002041d2ac5e483084.
In certain cases (maybe with 70 images?), the grid produces by running juxta with default values results in an image grid which is very narrow (2 images is observed) horizontally and consequently very tall vertically (oberserved 35 images).