I feel like the first thing I want to look at is the leftover files from 1.5x and 2.1.0.2
I'm wondering if these folders are still needed in 2.3.0.2 if not. I compared a fresh install to my folder directory and found some folders that were extra in my upgraded store. Should I delete them?
In Catalog/model
- admin/controller/amazon
admin/controller/amazonus
admin/controller/dashboard
admin/controller/ebay
admin/controller/fraud
admin/controller/openbay
In Admin/Model
- admin/model/amazon
admin/model/amazonus
admin/model/ebay
admin/model/openbay
- catalog/controller/amazon
catalog/controller/amazonus
catalog/controller/feed
catalog/controller/openbay
- catalog/model/amazon
catalog/model/amazonus
catalog/model/ebay
catalog/model/feed
catalog/model/fraud
catalog/model/openbay
catalog/model/sale