Got very strange behaviour and cannot pinpoint where the problem is.
Using composer on over 10 projects and having issue only on one.

Everything works with symlink strategy (used in local environments), but problem happens when switching to copy.

To replicate I am clearing all caches

rm -rf src/.modman/*
rm -rf vendor/*

then clearing composer cache and running composer without cache

COMPOSER_CACHE_DIR=/dev/null composer install

most of the extensions are installed and then one is complaining that source file is not there.

Error is

  copy(/home/marcins/workspace/Project/src/.modman/thirdparty_magext_commercelab_new/app/code/community/CommerceLab/GreatNews/Block/Settings.php): failed to open stream: No such file or directory

I've checked src/.modman/ folder and it looks like that particular file was checked out and then deleted by magento-composer-installer.
Code is there

vendor/magento-hackathon/magento-composer-installer/src/MagentoHackathon/Composer/Magento/Deploystrategy/Copy.php 

// If file exists and force is not specified, throw exception unless FORCE is set
        if (file_exists($destPath)) {
            if ($this->isForced()) {
                unlink($destPath);
            } else {
                throw new \ErrorException("Target $dest already exists (set extra.magento-force to override)");
            }
        }

I've checked that for sure target path does not exists in the project prior running composer

Can someone point me what is going on?
If I use composer cache - it will happen with other extension on composer list. Also this extension is used on other projects and composer works as expected.