You can get support for Neo by posting an issue on GitHub. First, check to make sure the bug you're reporting, feature you're requesting or question you're asking hasn't already been documented in the issues section. If it hasn't, the best course of action is to then open an issue.
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This is because when parsing the upload location, it applies any {property} tags to the fields' containing element. An asset field added to an entry will reference the entry, but an asset field added to a Neo block will reference the block. This is why the instructions change slightly when adding an asset field to a Matrix block - it says to use {owner.slug} instead of {slug}.
There are two ways around this. The first is to create a duplicate field that uses {owner.slug} instead of {slug} just for Neo block types.
The second is to use a little bit of Twig logic in your upload location. To begin, {slug} can actually be replaced with {{ object.slug }}. This shows that we have the ability to use double brace tags, which means we can use logic. So the idea is to check to see if object is a Neo block, and if so, use object.owner.slug instead. Normally this can't be done, but Neo provides a custom Twig extension that allows you test if some value is a Neo block.
In short, replace {slug} with {{ object is neoblock ? object.owner.slug : object.slug }}.
If your asset field is on a Matrix or Super Table field which is being used on a Neo block, you would instead need to check whether the owner of the Matrix block or Super Table row is a Neo block: {{ owner is neoblock ? owner.owner.slug : owner.slug }}.