गतिकारकोपपदात् कृत्

In a तत्-पुरुष समास a word ending in a कृत् affix preserves its original accent when preceded by an indeclinable called गति -- गतिश्च 1.4.60, or a noun standing in intimate relation to a verb (कारक) or any word which gives occasion for compounding (उपपद -- तत्रोपपदं सप्तमीस्थम् 3.1.92)
The above is according to Professor Bohtlingk. Thus प्रका꣡रकः, प्रक꣡रणम्, प्रहा꣡रकः, प्रह꣡रणम् ॥ The compounding is here by 2.2.18. With karaka-word we have :- इध्मव्र꣡श्चनः, पलाशशा꣡तनः, श्मश्रुक꣡ल्पनः 3.3.117. With upapada words, we have :- ईषत्क꣡रः, दुष्क꣡रः, सुक꣡रः ॥ All these are formed by लित् affixes and the accent is governed by 6.1.193. i. e. the word व्रश्चन is formed by ल्युट् (इध्मं प्रवृश्च्यते येन); so also with शातन (पलाशानि शात्यन्ते येन स दण्डः); so also with कल्पन (श्मश्रु कल्पते येन स क्षुरादिः) Why do we say "after a Gati, Karaka, or an Upapada word?" Observe देवदत्तस्यकारकः = देवदत्तकारकः ॥ Here the Genitive in देवदत्त does not express a karaka relation. The genitive is here a शेष लक्षणा षष्ठी denoting a possessor and not a कर्मलक्षणा one: for had it been latter, there would have been no compounding at all, by 2.2.16. see also 2.3.65. The word कृत् is employed in the sutra for the sake of distinctness; for a gati, karaka or upapada could not be followed by any other word than a krit-formed word, if there is to be a samasa. For two sorts of affixes come after a root (dhatu) namely तिङ् and कृत् ॥ A samasa can take place with krit-formed. words, but not with tinanta words. So that without employing कृत् in the sutra, we could have inferred that कृत् was meant. Therefore, it is said the 'Krit' is employed in the sutra for the sake of distinctness. According to this view we explain the accent in प्रपचतितराम्, प्रपचतितमाम्, by saying that first compounding takes place with प्र and the words पचतितर and पचतितम ending in तरप् and तमप् and then आम्, is added and the accent of the whole word is regulated by आम् by the rule of सतिशिष्ट (see 5.3.56 and 5.4.11. According to others, the कृत् is taken in this sutra, in order to prevent the gati accent applying to verbal compounds in words like प्र꣡पचति देश्यः, or प्र꣡पचति देशीयं 5.3.67, or प्र꣡पचतिरूपम् 5.3.66. The accent of these will be governed by the rule of the Indeclinable first term retaining its accent.