At that zoom, I really can't tell what is going on very well. The stealth tachyon beam emitters should be able to be revealed by your decloaker or whatever else, and then your other ships can kill it. Possibly there is a bug related to this, but I haven't heard anyone else mention it, so it's possibly some sort of strange edge case. If you're at a planet with a planetary cloaker, for instnance, those get perma-cloaker and can't be revealed until the planetary cloaker itself is destroyed...