If the warp yarn has this kind of fault, then an individual end looks like slub yarn. This uneven look of an individual end draws user attention at that particular place of the fabric. Since this look in an irregular pattern on the fabric surface, therefore it is not acceptable in the fabric.
Weft wise slub look results for some fabric length. A weaver can minimize this defect up to some extent by using two weft feeder in the loom during weaving. The yarn having low imperfection should be used to avoid this defect up to the optimum level. These defects are repaired during mending by eliminating the thick or thin place. These yarn are replaced by mender with same yarn through mending needle.