Conversion to html Error

1. What is the problem? Be very detailed.
I am trying to convert my programmed Excel File into html. However I get the following error message:
Error: 'float' object has no attribute 'strip'
What can I do to correct?
2. What app or server are you using and on what device and operating system? Include version numbers.
ODK Aggregate
Online Link:

3. What you have you tried to fix the problem?
Checked my document carefully. I never had this problem before.

4. What steps can we take to reproduce the problem?

I am happy to share my Excel file if helpful
5. Anything else we should know or have? If you have a test form or screenshots or logs, attach below.

Hi @Jan_Stein

you mean to xml not html because we convert from xls->xml.
Could you attach your form, it's difficult to tell what's wrong without a sample.