Rebalance continually fails with: "Temporary Channel Failure"

[davterra]

Two channels open. Both have roughly 600k sats in outbound, and trying to rebalance 300k sats from A to B.

I've tried numerous times, both leaving fee undefined, and by putting in various small numbers for fee.

It always finds a route, but the rebalance fails with the error "Temporary Channel Failure"

[apotdevin]

One of the channels in the route seems to not have enough capacity. Have you tried the advanced rebalancing? It tends to work better

[DocBrown101]

I have the same problem and just can't get any further.

[yuvadm]

Getting this error a lot, even in cases like these:

2021-07-12 19:49:59 info [THUB]: {
    "evaluating": [
        "\u001b[90m69x1x1\u001b[39m ★ ★ ★ ★",
        "\u001b[92mFOO\u001b[39m 112233. Fee rate: 0.00% (3)",
        "\u001b[90m64x3x0\u001b[39m",
        "\u001b[92mGOO\u001b[39m 445566. Fee rate: 0.00% (3)",
        "\u001b[90m69x1x0\u001b[39m"
    ]
}
2021-07-12 19:50:04 info [THUB]: {
    "failure": "TemporaryChannelFailure at 644x3x0 from FOO"
}

where FOO and GOO are two well connected nodes (both with each other as well as with my node), with a decent rebalance target and fees much higher than the fee rates described, and yet TemporaryChannelFailure comes up repeatedly.

What exactly does this error mean? Is this a temporary network failure due to downtime, or not enough liquidity? How can I use this information to attempt a successful rebalance?