Reduced test to bare minimum.
Searching for the reason of the problem it apears, that no update on extended table gets executed as 'store' flag of all fields is false. Setting 'store' to true didn't help as 'index' of those fields is wrong. If also fixing the 'index' the test passes but then a bunch of other tests fail.
Will try to search the history of sql info classes at which point this problem has been introduced to get an idea how to fix it.