Looks like at present around 15 percent of the bases we are landing at and selling to are 'dark' and have either not at any point been added to the EDDN crowd sourced database for Elite, or have incorrect information about markets. Most likely as a result of no one actually ever having been there.
How can you help?
If you're using the EDMC version of the Hutton Helper, look in EDMC and make sure your data is being pumped to some of the community sites like Inara, EDSM etc
If you're using the online helper, you can configure some of these websites to pull data as we do from Frontier servers by authenticating.
Then. When doing your mission. If you see a settlement and it is NOT in the event list. Go there! Mug and gin it. It will be in our raw data feed and the Hutorn Hamster is chomping through that list and making sure not one mug is missed.