Django collectstatic recollects module static files when deployed to Heroku - django

Question

My issue is that every time I deploy my code to Heroku, when collecting static, all the static files within modules are copied again, even if they haven't changed. This means my free amazon S3 bucket copy limit is being reached after just a few deploys because it is copying 400 files each deployment.
The issue must be with some Heroku setting because when running manage.py collectstatic in my IDE, it does not re-copy the files even when using the S3 bucket as default.
I have DISABLE_COLLECTSTATIC=1 in my heroku config vars, and set it in the heroku CLI to be doubly sure.
I have no idea why it is doing this. There's nothing useful in the deployment logs either. Any help would be appreciated.
This is the log:
Successfully compiled 1 referred SASS/SCSS files.
Debug mode is off.
386 static files copied, 106 unmodified.
The 106 unmodified files are the bootstrap SASS and a few others of my own. the 386 files are drom django admin and django-countries. Despite not changing, they are always copied. No settings swap seems to fix the issue.
Relevant parts of my settings.py:
STATICFILES_FINDERS = [
# Default finders
'django.contrib.staticfiles.finders.FileSystemFinder',
'django.contrib.staticfiles.finders.AppDirectoriesFinder',
# finders for sass files
'sass_processor.finders.CssFinder',
]
STATIC_URL = '/static/'
STATIC_ROOT = os.path.join(BASE_DIR, 'staticfiles')
STATICFILES_DIRS = (os.path.join(BASE_DIR, 'static/'),)
MEDIA_URL = '/media/'
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')
# Settings for AWS bucket
AWS_S3_OBJECT_PARAMETERS = {
'Expires': 'Thu, 31 Dec 2099 20:00:00 GMT',
'CacheControl': 'max-age=94608000',
}
AWS_STORAGE_BUCKET_NAME = os.environ.get('AWS_STORAGE_BUCKET_NAME')
AWS_S3_REGION_NAME = 'eu-west-3'
AWS_ACCESS_KEY_ID = os.environ.get('AWS_ACCESS_KEY_ID')
AWS_SECRET_ACCESS_KEY = os.environ.get('AWS_SECRET_ACCESS_KEY')
AWS_S3_CUSTOM_DOMAIN = f'{AWS_STORAGE_BUCKET_NAME}.s3.amazonaws.com'
AWS_DEFAULT_ACL = 'public-read'
AWS_S3_OBJECT_PARAMETERS = {'CacheControl': 'max-age=86400'}
STATICFILES_LOCATION = 'static'
STATICFILES_STORAGE = 'custom_storages.StaticStorage'
STATIC_URL = f'https://{AWS_S3_CUSTOM_DOMAIN}/{STATICFILES_LOCATION}/'

Answer 1

So I figured it out after some work.
Despite having used DISABLE_COLLECTSTATIC=1 in other django projects and things running smoothly, in this case it turned out to be the problem. When I thought it must be a heroku setting creating the issue I realised there could only be one setting that interferes with static collection.
Removing the setting from heroku has resolved the issue. Everything now copies correctly as it should.