You have correctly identified the issue: there seems to be a conflict between the initial press on spacebar for the DashedSentence controller in “in place” mode and the debugger being on for whatever reason. That being said, I have no idea what causes that conflict
In any case, the behavior you see when the debugger is off is the normal behavior, the one consistent with how the DashedSentence controller works, and the one that your participants will experience anyway. Passing a string to the blankText parameter will overwrite the two dashes: if you pass "Aperte espaço para avançar.", the text will appear on the page before the first press on Space; if you pass the empty string "" then the page will be blank until the participant presses Space
The debugger bug (ironically) skips the whole pre-spacebar display, whether it should show the standard two dashes, a custom message or just a blank page, and you will see the first word instead. I’ll work on fixing this (if I manage to identify the source of the bug) but in the meantime you should just keep it in mind when designing your experiment
Jeremy