Why Kobo add spaces between letters of first word?
I have KoboAuraOne and while reading KePub file I noticed that Kobo, sometime, add spaces between letters, of the first word in a line. Example will be on book in my language, so please forgive if you don't understand text. But visually it will be clear.

In the background is Sigil with opened "problematic" ePub. Problematic word is:
Фиренца.
In Sigil (ePub) there are no spaces.
Problematic line in KePub file also don't have spaces, and code look like this:
<p class="normalweb1"><span class="koboSpan" id="kobo.109.1">„Фиренца. </span><span class="koboSpan" id="kobo.109.2">Банкарски кланови су његови доброчинитељи. </span>...
But on Kobo, opened KePub file, there are spaces (like on picture above).
This is not the only word. It happens on every second page.
Is it problem with how Kobo "read" KePub and is there are any solution?
I copied original ePub on KoboAuraOne, and it doesn't have problem with spaces between letters (same settings, except ePub does not support adding weight on added fonts):
<a href="https://ibb.co/yR9yQ08"><img src="https://i.ibb.co/yR9yQ08/problem-blanko-znaka-e-Pub.jpg" alt="problem-blanko-znaka-e-Pub" border="0"></a>
Kindle Voyage don't have this problem, no matter the font or size.