I just got off a call with Instructure/Canvas support:
Canvas said that they could see a change in grade for all students (that have the orange dot). At one point all students received a 0 and then that 0 was removed for all students. When that happens, all students receive an orange dot.
There is a missing submission policy that might have triggered this during an import from a previous semester. Most likely what happened, after the import, the quiz kept the original due date and the missing policy was triggered, which gave everybody 0s. During an import, all of the students received a 0 for the lab. When the grades were reset, all students showed a false positive submission.
Solution:
In the future, during the import, don’t forget to remove the assignment due dates.
OR
You can turn off the missing submission policy until after the import and change to current semester due dates.