Once in awhile I bump into customers that use JWeb and would like to have the full JWeb application, not just the light version called "platform" that's included in the Junos images. To make your search less painful, here is a release combo that worked for me on the EX4200-24T:
JUNOS Web Management Platform Package [15.1R7-S6.3]JUNOS Web Management Application package [15.1A2.2]
There are recommendationa all over the place at Juniper and some say use jweb-ex-app-15.1A4.1 and some say otherwise. When downloading, you can't select JWEB as a product, but you can use this link:
Then select your Junos version and the appropriate JWeb packages are displayed. In this case (15.1), there are two since 15.1 requires a special release and later ones require the other.
Hope this helps someone 🙂
Could you please share "show system storage" output from your EX4200 running 15.1R7-S6 JunOS release?