Some notebooks appear as black squares on list, appear normal when opening them

On my Android phone, some notes some times appear as black squares on the Notebook or All Note Cards list, instead of showing the usual preview. This seems to happen randomly. I have about 150 notes, and sometimes 2 or 3 appear as these black squares. Even after running a sync they will still appear as these black squares. However, when I open these notes the content does appear properly. The only way to fix this is editing or modifying the note, then after I close it the preview will appear properly again. Could this problem be checked, please? It's very annoying to search for a note and not being able to locate it because it does not show the preview.

Thank you!

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