validation warns of errors in first length variant.
validation does not warn of any errors in other length variants.

steps to reproduce:
open a ts file in QtLinguist, turn on all validations, turn on length variant view. click [+] to add a Length Variant above or below a current translation, intentionally cause a validation warning in the top length variant, see the warning appear. Remove any problems with the top length variant. Now try the same on the bottom length variant, see that no warnings appear, nor does the message get the "!" indicator.

Length Variant is a powerful feature that I look forward to using soon. It is important for each translation to pass validation.