A Snake (Text) Stew

I’m finishing up my work on VAT 5, one of those Akkadian prayers. I’ve written before about this prayer against the evil of a snake. In the course of my research, I came across 80-7-19 rev:2’-15’. Richard Caplice published it in 1967. Unlike VAT 5, which contains only a prayer, 80-7-19 has a complete Namburbi ritual. Below is an abbreviated score of a few lines from both texts. I’m using VAT 5 as the baseline. VAT 5:16-21 is text A and across 80-7-19 rev: 7-10 is text B. For a couple of the lines I provide only the translation of text A but I translate both text A and Text B for most of them. Remember, this is from the petition portion of the prayer. In both cases an invocation precedes these lines and a conditional praise follows them. The petition of Text B goes on for several lines after the last line reproduced here. Text A has a personal identification section that text B lacks.
A)                        ina ḪUL MUŠ šá ina É-ia
B)              n]am-da-ru ḪUL MUŠ an-ni-i
A) On account of the evil of a snake which in my house
B) [I am in f]ear (ana-ku at-ta-nam-da-ru) of the evil of this snake
A) [  ]IGI-ru-ma bu-ru
B) [              ] bu-ú-ru
A) proceeds to hunt
B) [which] hunts [in my house]
A) DÙ-šú a-mu-ru-ma
B) DÙ-šú-ma
                  I saw.
A) pal-ḫa-ku ad-ra-ka
B) [              ]-ra-ka
I am in fear, anxiety
A) u šu-ta-du-<ra->ku ina ḪUL BI
B) u šu-ta-du-ra-ku / [       ḪU]L-šú
A) and constantly frightened. From this evil
B) and constantly frightened. May this evil
A) šu-ti-qa-an-ni-ma
B) ana UGU-ia a-a TE-a
A) save me!
B) not approach near me.
All this looks like it could be from the same prayer with but minor variations. But, and this is an important but, while both are addressed to Shamash, the remainder of the two prayers is quite different. Sure, they have a couple of other stock phrases in common but in different places and in differing orders.
Here’s Caplice’s translation of the prayer in 80-7-19 rev:2’-15’.

[Incantation: Šamaš gui]de of the black-headed folk,
. . . [who brou]ght every[thing into existence,]
. . . [whose co]mmand is unchangeable,
[whose assent] no [god] can alter,
[judge my case], render my decision!
[I am in]fear of the evil of this snake
[which] hunts [in my house],so that
[I am afraid,] frightened and terrified
. . . May its evil not approach me, may it not come near,
may it not press (upon me), may it not affect me!
[May the evil of this [snake] be 3600 miles distant from my person!
Avert from me [its evil], that I may sing your praise
. . . and those who look upon me may forever
(bless] you, Šamaš. Thus you recite three times.

Compare this with my tentative translation or VAT 5 (I would translate some of it somewhat differently today) and you’ll see that despite considerable similarity they are different prayers. Do they have a common predecessor? If so, is it discoverable? What are the markers? How much should we worry when we face an ancient text from a single source that it is part of a stew of likely related texts? When we see scattered commonalities between texts, should we think of intertextuality? Or should we only think of a textual stew?
Update: I forgot to mention that there are of the order of a dozen Akkadian Namburbi texts that deal with the evil of a snake. Of those, the prayers in VAT 5 and 80-7-19 have the most in common.
Reference:

Richard I. Caplice, “Namburbi Texts in the British Museum II,” Or, 36 (1967), 1-38, here 24-27, text #20