The publishing tool fails to combine files

[AdamLeonSmith]

Unfortunately I cannot provide the test data I am using as it is personal data.

Steps to reproduce
Redact two files containing different data (in this case, one from Spain, one from the US) from the same day
In the publishing tool, load both files
Publish the data

Expected behaviour
The file exported from the publishing process should contain both redacted datasets

Actual behaviour
Only one dataset is included. The following is visible in the console:

Uncaught TypeError: Cannot read property 'length' of undefined
at updateStats (index.html:1504)
at updateExposurePoints (index.html:1404)
at updateDateRange (index.html:1343)
at HTMLDocument. (index.html:1314)
at e (jquery.min.js:2)
at t (jquery.min.js:2)

[AdamLeonSmith]

Additionally, I have compared the two files and they are semantically/syntactically equivalent.