It worked for me, too.
But a few days ago it started to behave like described. And no, I haven´t installed another plugin or updated anything when it started to be that way.
Only after that I checked the updated to the latest JEM version but without a change.
If I understand correctly, the problem started already with JEM 2.3.0 (out of nothing or at least without no changes to your website).
Thereafter you updated JEM, hoping for a fix, but it did not help.
After all, it seems not related to the changes introduced by JEM 2.3.1 at least.