Two identical code snippets given on the same directory level, one gets pylint import error the other does not - importerror

Question

I have two tests, which both import the module to be tested. The code is exactly the same. One test gets an pylint import-error and the other does not.
Directory looks like this:
/root
/modules
init.py
module_to_test.py
/tests
/testcase one
test_one.py
/testcase_two
test_two.py
```
In the test code i used
```
BASEDIR = os.path.dirname(__file__)
ROOTDIR = os.path.abspath(os.path.join(os.path.join(BASEDIR, os.pardir), os.pardir))
sys.path.insert(0, ROOTDIR)
from modules import module_to_test.py
The two test code snippets are identical, yet i get an pylint import Error in one but not in the other.
i tried passing the path via the settings.json to pylint directly, i tried the init-hook method, but nothing seems to work. What am i not seeing?
Content of the test file:
pylint error message:
"{
"resource": "/c:/SourceTree/DIN743/p_test_DIN743/p_integration_kerbueberlagerung_1_test/p_integration_kerbueberlagerung_1_test.py",
"owner": "python",
"code": "import-error",
"severity": 8,
"message": "Unable to import 'p_DIN743'",
"source": "pylint",
"startLineNumber": 10,
"startColumn": 1,
"endLineNumber": 10,
"endColumn": 1
}"
´´´
# -*- coding: utf-8 -*-
import os, sys
BASEDIR = os.path.dirname(__file__)
ROOTDIR = os.path.abspath(os.path.join(BASEDIR, "../.."))
TOOLDIR = os.path.join(os.path.join(ROOTDIR, os.pardir), "tools")
sys.path.insert(0, ROOTDIR)
sys.path.insert(0, TOOLDIR)
import unittest
from p_DIN743 import m_DIN743
from tools import m_jsonhelper
class TestDIN743(unittest.TestCase):
#classmethod
def setUpClass(cls):
# change cwd
os.chdir(os.path.dirname(os.path.abspath(__file__)))
print("cwd changed to: {}".format(os.getcwd()))
# check if inputs.json & soll_outputs.json exist
if not os.path.isfile("inputs.json"):
print("inputs.json does not exist but is required!")
if not os.path.isfile("soll_outputs.json"):
print("soll_outputs.json does not exist but is required!")
# create test object
cls.__test_object = m_DIN743.DIN743()
cls.__test_object.Run()
cls.outputs = m_jsonhelper.loadjson("outputs.json")
cls.soll_outputs = m_jsonhelper.loadjson("soll_outputs.json")
def test_dicts(self):
self.maxDiff = None
self.assertDictEqual(TestDIN743.soll_outputs, TestDIN743.outputs)
if __name__ == "__main__":
unittest.main()
´´´