I think that xmodules 201908 does not work to any forum user for firefox because I tried it on two different machines and it does not work in either.
As he wrote commensal for Google Chrome works and in the forum almost all users use Google Chrome and therefore to them it works while for those who use firefox does not work.
Users who use ui vision for firefox are few because almost everyone uses Google Chrome for this reason you have few reports of problems I think to all users who use ui vision for firefox the xmodules 201908 does not work.
Is there a user who uses ui vsion for firefox with xmodules 201908 and works it properly?
Win8.1x64
Chrome - OK
Firefox - Not installed