Well I've seen many people saying Kakashi is just spamming Kamui and Kishi choose to forget Kakashi has low stamina but I'm pretty sure current Kakashi have been using the chakra Naruto gave him when he gave them all chakra. Here we see Sakura say they all still had some chakra but it only diminished in size
Kakashi had the cloak before Obito warped him
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, this means they still have more chakra than they would normally have, not much different from when Kurama first gave Kakashi more chakra and didn't have a cloak. Kakashi had the cloak before Obito warped him
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then he didn't when he was fighting Obito
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and since Kamui isn't a chakra absorbing jutsus, the chakra must have only diminished in size. So it's like when Kurama gave him chakra
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. Only think that isn't consistent is when Kakashi first joined Naruto and Bee with Guy, he used Kamui like 5x plus some chidori's before collapsing and then using it a few more times shortly after that.