I had to add a standard thread group to the .jmx to get it to work (even if the thread group has nothing in it).
If you disable or remove the standard Thread Group in the .jmx leaving only free form arrival thread groups,
the file will no longer pass validation and cannot be run or debugged.
Also of note is that verification will pass if you do not set the broken script as the 'start test with' .jmx it will only give a warning and show 'passed' status.
I guess it's trying to read the load configuration section of the GUI?
The use case of using only Free Form Arrivals thread group is not currently supported.
If you upload a secondary JMX script it will that does not pass validation it will show a yellow exclamation but will not fail the validation.
This is by design
BLAZEMETER PERFORMANCE TESTING
So I used your two files and below is what I found.
1) when you upload the working version first this sets the Start test with: FreeFormArrivals_Working.jmx
2) when you then upload the not working one you get the following:
3) the yellow Circle with the exclamation mark means the file had problems but as it is not selected as the primary jmx it does not cause the validation to fail.
4) this is expected and working as designed.
Currently the ability to use "bzm - Free-Form Arrivals Thread Group" is not a supported use case and the normal Thread group must be included in the JMX script.