second y-axis unexpectedly flipping (more negative toward the top of the graph)

When graphing this data set that contains a spike, the y-axis inverts. If I switch the y axis with the y2 axis, it works as expected. If I graph a subset of the data that does not contain the spike, it works as expected (although that changes the "minimum" of the data, which changes the slider settings, which changes the axis settings, but only in magnitude; the min is always less than the max anyway, so scale shouldn't matter.)


Here's some relevant code in case something jumps out that I'm doing wrong... I can include more code and the raw data set if nobody thinks this is already a known issue.

this is buggy:

output$DXGraph <- renderDygraph({
df1 <- DXDataSubset()
if (length(df1) > 1){
DXxts <- xts(df1,
order.by = as.POSIXlt(as.character(unlist(df1[, 'utc_datetime']))),
tz = "UTC")
dygraph(DXxts[,c('premium','mid.x')],
main = "Premium and Mid.x of DX data") %>%
dyAxis("y", label = "mid.x", valueRange = c(input$YAxisSlider[1],input$YAxisSlider[2])) %>%
dySeries('premium',axis = 'y2') %>%
dyOptions(connectSeparatedPoints = FALSE) %>%
dyOptions(animatedZooms = TRUE) %>%
dyRangeSelector()
}

this works:

output$DXGraph <- renderDygraph({
df1 <- DXDataSubset()
if (length(df1) > 1){
DXxts <- xts(df1,
order.by = as.POSIXlt(as.character(unlist(df1[, 'utc_datetime']))),
tz = "UTC")
dygraph(DXxts[,c('premium','mid.x')],
main = "Premium and Mid.x of DX data") %>%
dyAxis("y", label = "premium", valueRange = c(input$YAxisSlider[1],input$YAxisSlider[2])) %>% ###only change: changed premium <--> mid.x from the line below
dySeries('mid.x',axis = 'y2') %>%
dyOptions(connectSeparatedPoints = FALSE) %>%
dyOptions(animatedZooms = TRUE) %>%
dyRangeSelector()
}
})

Start with the dyAxis valueRange and dySeries axis='y2' calls in the provided R example, then reproduce the second-axis inversion using data containing a spike. Compare the behavior with the axes swapped and with the spike removed; done means the second y-axis keeps the expected ordering in all cases.