Issue with build_from_derived i.e its dropping variables even when its in spec and keep = TRUE

[researchase]

There is a issue with build_from_derived i.e its dropping variables even when its in the spec and keep =TRUE
eg:

library(metacore)
library(metatools)
library(admiral)
library(haven)
library(dplyr)
library(lubridate)
library(stringr)
library(safetyData)

load(metacore_example("pilot_ADaM.rda"))
ADVS_spec <- metacore %>% select_dataset("ADVS")
spec_loc <- # SET STUDY SPEC PATH
VS = sdtm_vs
ADSL = adam_adsl

#get data :
ds_list <- list(ADSL=ADSL,VS=VS)

ADVS <- build_from_derived(
ADVS_spec,
ds_list,
dataset_name = NULL,
predecessor_only = FALSE,
keep = TRUE
)