Able to submit the file.
2 things I have done :
1.Raise the issue with IRCC through webform
2. Fresh attempt after clearing the browser cache.
Which one worked I don't know. But clearing the cache is must.
Hope it might help.
You can twerk the system. If you dont have any travel for your child or your spouse, remove the Not Applicale or NA. just leave it empty and your travel form will be ready to submit. next you confirm your backgorund form and then your family information form and then your generic form. This will activate all your form. Just remove any NA or Not Applicable from the travel form