Hi Hephaistos,
The warning 'incompatible font data XML' is normal. It informs you that the sbs you are using was made from a previous version so Designer updates it and displays this message as the result of the update.
I will make some tests with bricks_terra_blend_irregular.
Trilo, can you give me names of sbsar which make Designer crash (downloaded on source and share) ?
For both of you, you are on 6.0.2 so did you send a crash report ? If yes, what's your mail, I will search your for your crash report (for this, answer me by PM

)