node_modules directory not created when using npm install during AWS CodeBuild

After the CodeBuild is complete and I ssh into my environment, I can see that the server app's dependencies are installed and found in its node_modules. However in the client directory, there is no node_modules nor build directory. In the build logs, npm install --prefix client --production appears to run fine.

My question is almost exactly like this one, except it is both the node_modules and the build folder.

Is there a problem with the buildspec file? Here it is (EDIT 4: updated)

version: 0.2

phases:
  install:
    commands:
      # upgrade AWS CLI
      - pip install --upgrade awscli
      # install Node 12
      - curl -sL https://deb.nodesource.com/setup_12.x | bash -
      - apt install nodejs

  pre_build:
    commands:
      # install server dependencies
      - npm install
  build:
    commands:
      # install client dependencies and build static files
      - npm install --prefix client && npm run build --prefix client

  post_build:
    commands:
      - ls -la
      - ls client -la

artifacts:
  files:
    - '**/*'

EDIT 1: here's an example of what the codebuild logs show for the npm install --prefix client:

Running command npm install --prefix client --production



> [email protected] postinstall /codebuild/output/src133125934/src/client/node_modules/babel-runtime/node_modules/core-js
> node -e "try{require('./postinstall')}catch(e){}"

And for the npm run build -prefix client:

[Container] 2020/07/02 00:24:06 Entering phase BUILD
[Container] 2020/07/02 00:24:06 Running command npm run build --prefix client



> [email protected] build /codebuild/output/src133125934/src/client
> react-scripts build



Creating an optimized production build...
Compiled successfully.



File sizes after gzip:



  144.95 KB  build/static/js/2.d25271aa.chunk.js
  23.22 KB   build/static/css/main.fe6e5073.chunk.css
  6.38 KB    build/static/js/main.8e99a285.chunk.js
  774 B      build/static/js/runtime-main.f63e6028.js

EDIT 2: Using ls to see the directories after the build:

[Container] 2020/07/02 01:11:24 Entering phase POST_BUILD
[Container] 2020/07/02 01:11:24 Running command ls -la
total 136
drwxr-xr-x  12 root root  4096 Jul  2 01:09 .
drwxr-xr-x   3 root root  4096 Jul  2 01:09 ..
drwxr-xr-x   2 root root  4096 Jul  2 01:09 .ebextensions
-rw-rw-r--   1 root root   130 Jul  2 01:08 .gitignore
-rw-rw-r--   1 root root    16 Jul  2 01:08 .npmrc
-rw-rw-r--   1 root root    34 Jul  2 01:08 README.md
-rw-rw-r--   1 root root  1737 Jul  2 01:08 app.js
drwxr-xr-x   2 root root  4096 Jul  2 01:09 bin
-rw-rw-r--   1 root root   566 Jul  2 01:08 buildspec.yml
drwxr-xr-x   6 root root  4096 Jul  2 01:10 client
drwxr-xr-x   2 root root  4096 Jul  2 01:09 config
drwxr-xr-x   2 root root  4096 Jul  2 01:09 graphql
drwxr-xr-x   2 root root  4096 Jul  2 01:09 models
drwxr-xr-x 197 root root  4096 Jul  2 01:10 node_modules
-rw-rw-r--   1 root root 63888 Jul  2 01:08 package-lock.json
-rw-rw-r--   1 root root   814 Jul  2 01:08 package.json
drwxr-xr-x   2 root root  4096 Jul  2 01:09 routes
drwxr-xr-x   2 root root  4096 Jul  2 01:09 services
drwxr-xr-x   2 root root  4096 Jul  2 01:09 views




[Container] 2020/07/02 01:11:24 Running command ls client -la
total 748
drwxr-xr-x    6 root root   4096 Jul  2 01:10 .
drwxr-xr-x   12 root root   4096 Jul  2 01:09 ..
drwxr-xr-x    3 root root   4096 Jul  2 01:11 build
drwxr-xr-x 1081 root root  36864 Jul  2 01:10 node_modules
-rw-rw-r--    1 root root 699332 Jul  2 01:08 package-lock.json
-rw-rw-r--    1 root root   1212 Jul  2 01:08 package.json
drwxr-xr-x    2 root root   4096 Jul  2 01:09 public
drwxr-xr-x    8 root root   4096 Jul  2 01:09 src

EDIT 3: After verifying the directories are made, I ssh into the beanstalk (ec2) instance to check if they have been deployed but this is what I get:

$ cd /var/app/current
$ ls
app.js
bin
buildspec.yml
client
config
graphql
models
node_modules
package.json
package-lock.json
Procfile
README.md
routes
services
views

$ cd client
$ ls
package.json 
package-lock.json 
public 
src

The build and modules directory are not deployed into beanstalk.