When translating the Kleisoura (Byzantine district) from English to Spanish, the Lang-el template on the first paragraph is adapted when added to the translation (i.e., the equivalent template in Spanish is added with the information). However, an additional ":" character is added after the template in the target language:
This extra ":" character seems to come from the rendering of the source template. The way a template is rendered should not interfere with the contents, so it is unclear how the ":" leaked from there into the target contents.
This happens with Apertium (and possibly with other plain text MT systems).