I too do not have observered a readme for IS_9.9_Core_Fix2 yet.
Do you mean MWS_9.9_Fix2 by chance?
There should not be any transactions and tpa´s available when this is a complete fresh install incl. database schemata.
There might be some default DocTypes but I am not sure.
So if you have transactions and tpa´s available, from where do they come (Onboarding Partners?)?
That is strange… I was able to install it on the 29th March.
Initially I did face issues trying to install it using Command Central, but then I was able to successfully install it using Update Manager.
It looks like the Core Fix2 was recalled and is being replaced by 9.9 Core Fix 3. This fix is scheduled to be released on 6/27. Once installed, I’ll confirm (or not) if it has resolved this issue.