Combining exchange volumes results in shortest history

Btcusd has longest timeline (pre-2017).
Btcusdt has shortest timeline (beginning june 2021).
When I try to combine all 3, it only shows the total of the shortest timeline.
How can I get it to show longest timeline with everything combined??

###### THE SCRIPT

//@version=4
study(bitstamp BTC VOL TOTAL)

btst = security(bitstamp:BTCUSD, timeframe.period, volume)
btstc = security(bitstamp:BTCUSDC, timeframe.period, volume)
btstt = security(bitstamp:BTCUSDT, timeframe.period, volume)
btst1 = btst + btstc + btstt

plot(title=allexchanges, series= btst1, style=plot.style_line, color=color.blue)

Hi there

Maybe try adding the barmerge.lookahead_on parameter
Documentation: https://www.tradingview.com/pine-script-reference/v4/#fun_security

Thanks for responding :)
I tried lookahead with no luck then added gaps. also no luck.

btst = security(bitstamp:BTCUSD, timeframe.period, volume, gaps=barmerge.gaps_on, lookahead=barmerge.lookahead_on)
btstc = security(bitstamp:BTCUSDC, timeframe.period, volume, gaps=barmerge.gaps_on, lookahead=barmerge.lookahead_on)
btstt = security(bitstamp:BTCUSDT, timeframe.period, volume, gaps=barmerge.gaps_on, lookahead=barmerge.lookahead_on)