As we can see here[
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], Naruto's seal is represented by the swirling pattern. This also shows that the seal becomes present when Naruto's body is trying to tap into Kurama's power in some way, and fades when it's got what it's wanted.
As we can see here[
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], the seal becomes visible while Naruto is in KCM, and later BCM, because he's one again tapping into Kurama's power. We know this new marking is the seal because Naruto makes direct contact with it in order to lock away Kurama's power, or in other words, seal it away. Naruto has just modified the seal because he's got the key now and this modified seal allows him to access Kurama's power.
As we can see here[
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], the seal is still intact, but further modified. No matter what form Naruto takes, the spiral form that indicates the seal is still there[
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], just in a new way to indicate his further progress with control of the seal. This shows that despite being a Perfect Jinchuriki, his seal is still intact.