Once, I gave a peirush on Eiqev based upon a Rashi technique used somewhere else - during a speech at another shul.
One concerned fellow asked, ""How can you set aside what Rashi says here - in favour of an approach he uses elsewhere"? He meant that Rashi implicitly disputed my interpretation.
To me, the answer is simple, Rashi is not exhaustive. He only gives a subset of all the possible p'shatim that even he might have brought forth. Don't assume that Rashi objects to another approach just because he omits it.
There's a "Proof-Text" for my approach. Rashi gives one explanation for the word "Yassaf" in Vayeishev (38:26), "v'lo yassaf od l'daatah". However, Rashi's gives a second explanation in B'haalotcha. (11:25) Relying on the Targum Onkelos concerning Eldad and Meidad, Rashi interprets "Yassaf" to mean "v'lo Passaq".
Here, the Local Targum says otherwise! It seems to mean "V'lo Ossif". Sh'ma Mina - Rashi wished to bolster his own reading of the p'shat here even though the local Targum interprets the words differently.
I did the same thing. Although the local Rashi explains things differently, I used Rashi's explanation in Eiquev. I used Rashi to give p'shat in Eiqev from a non-local Rashi despite the local Rashi saying otherwise.
It's still possible that the local Rashi disagrees with his other interpretation. We can't know for sure. However, since Rashi himself used the technique, it's legitimate for us to use it as well.