A problem in libreoffice with persian language

Hello, I think there is a bug in libreoffice with persian language.
I’m trying to write a technical text in libreoffice in farsi(persian) language.
whenever i try to have inline formulas, like lambda/4 or L_r it is shown very poorly in final pdf. (it is not shown correctly). I don’t use any extensions but the default formula editor of libreoffice and I export it as pdf by libreoffice default. could any developer please see this? I don’t have this problem in open office but it exists in libreoffice.
I don’t have this problem with english language either. it just happens when I try to type persian. the problem doesnt exist in the odt format. just when I try to convert it to pdf. (which is important btw) Here is a picture:


as I said the .odt format doesn’t have problem. the PDF format is corrupt. to reproduce do this: File > Export as > Export as PDF.