MAGETWO-94462: Configurable product thumbnail images slow to generate when high number of thumbnails (14+) in vertical navigation

Author: yelahin-serhiy

lib/web/fotorama/fotorama.js

@@ -2562,7 +2562,7 @@ fotoramaVersion = '4.6.4';
                     thisData.t > rightLimit : thisData.l > rightLimit;
                 specialMeasures.w = thisData.w;
 
-                if (thisData.l + thisData.w < leftLimit
+                if ((opts.navdir !== 'vertical' && thisData.l + thisData.w < leftLimit)
                     || exceedLimit
                     || callFit(thisData.$img, specialMeasures)) return;