Missing chars in ticket creation from email

When we import and create a ticket from an email, there are missing some specific characters in the subject.

Email subject what is sent:
Start aéaÉaáaÁaűaŰ aőaŐaúaÚa aöaÖaüaÜaóaÓa aíaÍa 2 End

and the result in Livezilla client after a ticket creation:
Start aéaÉaáaÁaűaŰ aőaŐaúaÚa aö aaaaaa aaa 2 End

As you can see, there are missing these characters: ö Ö ü Ü ó Ó í Í

The source of the sent email (some private datas deleted):

From: xxxx
Subject: =?UTF-8?B?U3RhcnQgYcOpYcOJYcOhYcOBYcWxYcWwIGHFkWHFkGHDumHDmmEgYcO2?=
=?UTF-8?B?YcOWYcO8YcOcYcOzYcOTYSBhw61hw41hIDIgRW5k?=
To: support@xxxx.yy
Message-ID:
Date: Fri, 15 Dec 2017 18:14:32 +0100
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0)
Gecko/20100101 Thunderbird/52.5.0
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: hu
Content-Transfer-Encoding: 8bit

Enviroment:
Livezilla server: 7.0.8.9 (Centos, Apache, MySQL)
Livezilla client: 1.2.2 (OSX)

Thank you!