Box Select tool disappears randomly

When streaming data, I can select the “Select Box” or “Lasso select” option and use it. However, it disappears after a while, and I don’t know how to get it back. It stays in the selection mode, but if I switch to “Zoom” or “Pan”, I’m unable to go back into a selection mode. Does it have something to do with extendTraces? Here is a codepen example.

Ah, that’s because we don’t support lasso and box selection for scatter traces with mode: 'lines'.

At the beginning of the stream, your traces have mode: 'lines+markers' which supports selections, but once they have enough points the default mode becomes 'lines' which no longer support selections

Setting mode: 'markers+lines' in both your traces to start should solve your problems.