Customize field can not save

I customize a field in the custom question with =sum(field A)/distinct(field B)
At the beginning , I can get the result. And then, I refresh the result , but it can not display result any more.

I click the “Save” button, but it seems not work.

I debug it with browser, and get these error.

How can I fix it, Thanks for any help!

Hi @aliks
Upgrade to 0.33.4, where it’s fixed. The work-around is to give the Custom Field a name, then the interface will work again.

Thank for your help, it works now.