Exact same problem here.
I did some investigation and I can confirm the following:
* Eterm (0.9.6-1) runs properly on AntiX-15 which is based on Jessie.
* I installed (with dpkg) on Jessie the Eterm deb package that runs properly on AntiX-15 and Eterm still exhibits the same erratic behaviour [on Jessie].
* I installed on AntiX-15 the Eterm deb package that behaves erratically on Jessie, and it runs properly [on AntiX-15].
* I repeated the latter two above steps between AntiX-15 and Stretch (testing) and AntiX-15 and Sid with identical results as with AntiX-15 and Jessie: - AntiX-15 runs the Stretch and Sid Eterm packages properly, whereas Stretch and Sid exhibit erratic behaviour on the Eterm package brought over from Antix-15.
The above led me to speculate that there is nothing wrong with the Eterm package per se, instead, the problem seems to lie with Jessie and subsequent (Stretch, Sid) system implementations.