we have an setting for that: Settings-> Cover Fetch Depth
if you pick the slowest option you will get the correct image
slower = more accurate, but it will be slow for large archives
archives are not guaranteed to be stored in alphabetical order. Your archive viewer actually sorts them for you after examining the archive contents. For large archives this process can be really slow thats why we have that setting! Let me know if it works for you.
I did not know this function because in the french version of app the translation is not right. "Fetch épaisseur" could be "Affichage aperçu couverture". I know that because I am french, so sorry for my english !
This choice of function is really necessary ? It is not better to wait more time than to have an incomplete information ?