PhpStorm Composer always says it fails, but it has no errors

Question

I run a PhpStorm remote development instance on my dev server.

When I use Composer from there, then it always says "something failed" with ANY Composer command (I have tested "validate", "diagnose", "install", "update", ...).

Example output from "diagnose"

diagnose --no-interaction --ansi --verbose
 Checking composer.json: OK
 Checking composer.lock: OK
 Checking platform settings: OK
 Checking git settings: OK git version 2.25.1
 Checking http connectivity to packagist: OK
 Checking https connectivity to packagist: OK
 Checking github.com rate limit: OK
 Checking disk free space: OK
 Checking pubkeys: 
 Tags Public Key Fingerprint: xxx
 Dev Public Key Fingerprint: xxx
 OK
 Checking Composer version: OK
 Checking Composer and its dependencies for vulnerabilities: OK
 Composer version: 2.8.5
 PHP version: 8.0.14
 PHP binary path: /usr/bin/php8.0
 OpenSSL version: OpenSSL 1.1.1f  31 Mar 2020
 curl version: 7.68.0 libz 1.2.11 ssl OpenSSL/1.1.1g
 zip: extension present, unzip present, 7-Zip present (7z)
 Composer diagnosed some issues in ./library/composer.json.

If I run the Composer command in a SSH shell (bash) or within PhpStorm "Terminal" I get no errors.

I also tested, if the return code of Composer is maybe not returning "success" so I added an && echo 'XX which was printed out, so no error return code.

I have no clue what PhpStorm diagnoses here.