Erratic behaviour in a makefile resulting in re-building targets - makefile

Question

I'm using makefiles to structure a data analysis pipeline consisting of various steps such as extracting data, sampling and modelling. However, when I create an additional "upper-level" makefile (such as modelling) that depends on others, and I try to run make again (either on the new makefile or any other upper-level makefiles), it tries to re-build everything again from the lowest-level makefile targets.
In the code below I show the "lowest level" makefile and another one (makefile.sample that includes the first one):
Makefile
all:
make $(DATA_TRN)
make $(Y_TRN)
# dates
SNAP_TRN := 2019-06-18
SNAP_TST := 2019-07-24
# Targets
TARGET_CLASS = m1_vol
TARGET_SURV = m1_qty
TARGET_INIT = act_qty
END_DUR = 1
# dirs
DIR_DATA := data
DIR_CONFIG := configs
# data files for training and predict
DATA_TRN := $(DIR_DATA)/processed/churnvol_train_$(SNAP_TRN).csv
DATA_TST := $(DIR_DATA)/processed/churnvol_test_$(SNAP_TST).csv
# labels
Y_TRN := $(DIR_DATA)/processed/label_train_$(SNAP_TRN).csv
Y_TST := $(DIR_DATA)/processed/label_test_$(SNAP_TST).csv
# Config files
CONFIG_PANEL := $(DIR_CONFIG)/config_panel.yaml
CONFIG_INPUT := $(DIR_CONFIG)/config_inpute.yaml
FEATS := $(DIR_CONFIG)/featimp_churnvol.csv
# Generates a clean dataset (inputed and one hot encoded)
$(DATA_TRN): $(CONFIG_INPUT) $(FEATS) | $(DATA_DIR)
python src/_buildDataset.py --train-file $(DATA_TRN) \
--test-file $(DATA_TST) \
--train-date $(SNAP_TRN) \
--test-date $(SNAP_TST) \
--config-panel $(CONFIG_PANEL) \
--config-input $< \
--feats $(lastword $^)
$(Y_TRN): $(DATA_TRN) | $(DATA_DIR)
python src/_extractColumns.py --data $< \
--columns $(TARGET_INIT),$(TARGET_CLASS),$(TARGET_SURV) \
--file $#
clean:
-rm -rf $(DATA_TST) $(DATA_TRN) $(Y_TRN) $(Y_TST)
.PHONY: all clean
Makefile.sample.u1
include Makefile
sample:
make -f Makefile.sample.$(SAMPLE_NAME) $(DATA_TRN_SAMPLE)
SAMPLE_NAME = u1
MIN_RATIO = 0.333333 # ratio of minority class for undersampling
DATA_TRN_SAMPLE := $(DIR_DATA)/processed/churnvol_train_$(SAMPLE_NAME)_$(SNAP_TRN).csv
$(DATA_TRN_SAMPLE): $(DATA_TRN) | $(DATA_DIR)
python ./src/_generate_sample_u1.py --data-train $< \
--data-file $# \
--min-ratio $(MIN_RATIO) \
--end-feat $(TARGET_SURV) \
--end-dur $(END_DUR)
.PHONY: sample
From these 2 makefiles, I'm assuming that make only needs to rebuild $(DATA_TRN) if either $(CONFIG_INPUT) or $(FEATS) changed after $(DATA_TRN) right? The problem is that both timestamps show a previous date from the target $(DATA_TRN) and when I run make all it still rebuilds the target. src/_buildDataset.py also shows a previous date. I've tried to debug and running make $(DATA_TRN) returns a $(DATA_TRN) is up to date. message. However, when I run make $(Y_TRN) it rebuild $(DATA_TRN), which I find odd. This also means that when I run make -f Makefile.sample.u1 sample, it also goes on to rebuild $(DATA_TRN). Can someone help me figure out if I did something wrong? Or other ways to debug, such as knowing exactly what file make marked as "changed". Thank you