Consider the Lexis diagram below:

In order to achieve this under the current version, I use the following code:

age_start = 15

lexis_grid(year_start = 2018,
           year_end = 2026,
           age_start = age_start,
           age_end = 23,
           lwd = .1,
           delta= 1) %>%
  
  lexis_cohort(2004 + age_start)

In order for this plot to display correctly, I need to add age_start to the cohort parameter of lexis_cohort. This behavior is unexpected.