Here are a couple of companies visible in your old API but not the beta. Both were incorporated on 12-Jul-2017. Did you have a glitch that day?
NELCON MERCHANTS (UK) LTDhttp://data.companieshouse.gov.uk/doc/company/SC571054.html
M.P.I. LOGISTICS LTDhttp://data.companieshouse.gov.uk/doc/company/10862631.html
and here's one more, incorporated on 3-Apr-2018:
DOGAN FOOD LTDhttp://data.companieshouse.gov.uk/doc/company/11286395.html
These have been investigated and are now available on Beta/API.Thank you for taking the time to report ALL the issues you have found over the last few weeks.They are all being investigated and we do very much appreciate your help.
This one (11286395) has been identified along with others as requiring a little more work to correct, but it will be corrected in the next 48 hours.Again, thank you for taking the time to report these issues.