Ultimately or in the final analysis; when it comes down to it.
归结到根本上。
清·张南庄《何典》第二回归根结柢，把一场着水人命一盘摙归去，还亏有钱使得鬼推磨。”
When you get down to it, the problem is a lack of communication.
Learn the next connected idiom: 归根到底 (guī gēn dào dǐ) → 地广人稀 (dì guǎng rén xī)
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