Originally Posted by
Thorsten Heinsight To identify the root of the problem, a quick google search tells me that the Slovenian word for 'bracket' is 'oklepaj' so I'm guessing this is a default word substitution set on the device in Settings > Language and Input > Prediction and Correction > Word Substitution. I assume there is a similar word related to brackets that starts with 'do'? Either removing these default word substitution or, as baarn said, mapping a new word substitution should fix your problem.
It's interesting that you say this issue persists on 10.3.1 because I know on 10.2.1 "br" used to be a default word substitution that changed to a bracket, but they took it out of the default list on 10.3.1 as far as I can tell, so I'm surprised they didn't do the same for the Slovenian equivalent.