Generation on 'URLs' is possible only once

[DaryaGurtovenko]

The issue is right after uploading the list of URLs button 'Generate several pages' works and pajeobjects file is downloaded but after this first time the button doesn't do anything (it still looks available).

Preconditions:
JDN is installed
Dev console is closed

Steps to reproduce:
1 Open Dev console and go to JDN
2 Jump to 'URLs' tab
3 Tick some pages
4 Click 'Generate several pages'
5 Tick/untick some pages (but one still must be ticked)
6 Click 'Generate several pages' once again

Actual result:
No files are downloaded for the second and another times.
Only closing and re-opening of Dev console helps here
It's the console output:

Expected result
Generate should be successful