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Hmmm thank you for the feedback. Google is not indexing these though...

If I google a phrase "egardwatches.com  filter 128" to find this url  -http://www.egardwatches.com/shop/?filter_additional-features=128 -

It does not appear in Google results, and it has the ? query indicator, which should tell Google it is dynamic?

Are you sure this isn't an issue with Moz crawl only?

How can it be duplicate content if it isn't even indexed?

1. I personally would concentrate on your Title tags, modifying the title tags to reflect your researched keywords will have a relatively quick turnaround if optimized correctly. If your CMS allows, change the whole structure to stay within Moz/Google suggested limits. Add unique content to your category pages, and optimize those titles as well.

2. Compress images, caching, server optimizations, etc to increase website speed as much as possible, an increase usability.

3. Gain low hanging fruit quality relative links, for example, any links to industry brand lists, any brand mentions without links, charity sponsorships without links etc.

I'm getting 100's of Duplicate Content warnings for a Woocommerce store I have. The urls are 
 etc

These don't seem to be indexed in google, and the canonical is for the shop base url. These seem to be simply urls generated by Woocommerce filters.

Is this simply a false alarm from Moz crawl?