File not found, but appears in directory - docker

Question

I am trying to run a docker build command to set up a container. When I run it, a file I need can't be found. I receive this error
/bin/sh: 1: ./downloadScript: not found
The command '/bin/sh -c ./downloadScript' returned a non-zero code: 127
I run ls -la before the script should run and it appears.
drwxr-xr-x 1 root root 4096 Apr 30 18:05 .
drwxr-xr-x 1 root root 4096 Apr 30 18:05 ..
-rwxr-xr-x 1 root root 714 Apr 29 18:20 downloadScript
drwxr-xr-x 4 root root 4096 Apr 30 18:05 gradleProject
I've tried a few things
chmod 777 the file and directory
cp the file, the chmod the new one (this new file can't be found either)
reset docker credentials
My current script:
...
WORKDIR /dir1
RUN ls -la # For manual verification
RUN ./downloadScript
...
Docker output
Sending build context to Docker daemon 120.3kB
Step 1/17 : FROM openjdk:8-slim as builder
---> e2581abdea18
Step 2/17 : WORKDIR /dir1
---> Using cache
---> 4ef289b22b45
Step 3/17 : ADD WCE_Docker/res /dir1
---> Using cache
---> 3d757ec6caba
Step 4/17 : ADD /GradleProject/ /dir1/gradleProject/
---> Using cache
---> 7e46cc77290d
Step 5/17 : WORKDIR /dir1
---> Using cache
---> fe7570221d31
Step 6/17 : RUN ls -la
---> Using cache
---> 019ef7d640da
Step 7/17 : RUN ./downloadScript
---> Running in 9870fd1e3af3
/bin/sh: 1: ./downloadScript: not found
The command '/bin/sh -c ./downloadScript' returned a non-zero code: 127
It runs correctly on Mac and Ubuntu, but not on Windows 10.
Update
I manually setup the container and attempted to run the script and received a slightly different error.
root#835516a24a7f:/dir# ./downloadScript
bash: ./downloadScript: /bin/bash^M: bad interpreter: No such file or directory
Which I've found is DOS based line ends. I am going to fix that then post results.
Update Results
Ran dos2unix downloadScript and it worked correctly. The problem was DOS line ends.