This bug has been present since 7.0.
[ In the past instead of crashing, it would probably have hit a serialization exception instead ]

One or more of the files being read in the child query, do not match the defined record structure.
Specifically, if the 1st requires translation, but subsequently another doesn't, then it hits this problem.

The workaround for now, is to check and ensure that the logical files being read in a CQ like this, either all need translation, or none do.