Thank you all for responses! I think my problem is same as this one:
“[SOLVED] [memory leak] [master branch] I face a problem when call lv_label_set_text() function periodicity to refresh date]”
https://forum.lvgl.io/t/solved-memory-leak-master-branch-i-face-a-problem-when-call-lv-label-set-text-function-periodicity-to-refresh-date/90/16