kdasari
It is often said that mantras are cursed and therefore require some type of specific ritual action (pūjā) or another set of specific curse removal mantras to make them effective. This is a very orthodox and traditional point of view which is for the most part not followed in contemporary paramparās that impart dīkṣā, such as ours.
However, that being said, many tantras (both Śaiva and Vaiṣṇava) describe such imperfections and "defects" of mantras. The Kulārṇava tantra describes sixty such faults that can affect mantras such as being "asleep", "terrifying", "fruitless", "devoid of a limb", and even "diseased." Other tantras describe mantric imperfections as having to do with an inauspicious number of syllables and the placement of certain syllables in an order that is not conducive to attainment. More blatant examples include, hearing a mantra by accident, or reading it in a book, both require extra rituals to re-empower them. A little more specialized and esoteric is the recommendation that certain mantras are not to be chanted aloud and so if they are spoken, they are already rendered defective and need to be "fixed." Sometimes these fixes involve extended recitation.
Of course, many will likely wonder how in the world can a mantra, which is divine in nature and transmitted through tradition be given as deficient, wouldn't that mean that the tradition itself is deficient?
It is a perfectly legitimate question. A mantra might be thought to be defective because mantras (which are often given in code) are interpreted, or rather "extracted" slightly differently according to different traditions. If one wants to venture further, one might even say "incorrectly."
Another reason a mantra might be thought to be defective or cursed is that it is simply too powerful for common people and so sages who attained siddhi with it cursed such a mantra so the average person will not be able to misuse its śakti. This is a very popular explanation that can be found throughout our Purāṇas.
As admin wrote, in Guruji's tradition (at least as far as I have understood it!) the grace of Śrī Guru who imparts the mantra removes all defects, "curses," and imperfections that may exist and gives the śiṣya a priceless and flawless gem, ready to be polished daily with mantra japa.
śrī gurubhyo namaḥ