Freetype font gets freed or garbage collected?


I’m running micropython 1.22 on the unix port-
I’m creating lvgl font’s using the lv_freetype wrapper:

ISEW.ISew.font_normal_14 = lv.freetype_font_create \
            ( "fonts/Rajdhani-Bold.ttf"

When I use the font at the beginnig everything works as expected (for debugging purposes I added a print statement in lv_font_get_glyph_width.

printf ("Font %p, lh=%d, letter %d\n", font, font->line_height, letter);

Font 0x7ffff6ad32a8, lh=18, letter 50

But at some point the system crashes with a segfault and the printf statement just before the crash shows that the font data is corrupted:

Font 0x7ffff6ad32a8, lh=1434156016, letter 83

Program received signal SIGSEGV, Segmentation fault.
0x000055555566b0e2 in lv_font_get_glyph_dsc (font_p=font_p@entry=0x7ffff6ad32a8, dsc_out=dsc_out@entry=0x7fffffffc9f0, letter=letter@entry=83, letter_next=letter_next@entry=101) at /data/fast/lvgl/lvgl/src/font/lv_font.c:69
69              bool found = f->get_glyph_dsc(f, dsc_out, letter, f->kerning == LV_FONT_KERNING_NONE ? 0 : letter_next);

I than tried to use the online font converter and use these fonts instead and the segfault is gone.

So I have no further idea whats happing here.
Any idea would be welcome.