Brachot that do not begin with "Baruch Atah" are generally supposed to follow another Beracha (see Berachot 46a, Mishneh Torah, Berachot 11:1 for more information).
If one is in the middle of reciting one, and then realises that the preceding beracha was invalid for some reason (beracha levatala, beracha she'en tzericha, not pronounced properly etc.), what should one do assuming they haven't said Baruch Ata Ado-nai at the end yet?
In the case that they are not a beracha hasemucha lachaverta, maybe the halacha is to continue (what if it is?), but as one hasn't said Baruch Ata Ado-nai yet, perhaps they are supposed to stop.