Your company staff is well known among our club members for its quality but the only apparent flaw we can detect is that they only speak English.

apparent 是形容词，由动词 appear（出现、显现）加上后缀 -ent 构成，意思是"显而易见的、表面上的"。在这里指"能够被轻易察觉到的"缺陷。