When translating the [[ https://en.wikipedia.org/wiki/Kleisoura_(Byzantine_district) | Kleisoura (Byzantine district) ]] from English to Spanish, the [[ https://en.wikipedia.org/wiki/Template:Lang-el | Lang-el ]] template on the first paragraph is adapted when added to the translation (i.e., [[ https://es.wikipedia.org/wiki/Plantilla:Lang-el | the equivalent template in Spanish ]] is added with the information). However, an additional ":" character is added after the template in the target language.
{F31777859, size=full}
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).