Is it possible to incur slippage during demo trade and backtesting?

Hi guys, I was wondering whether it is possible to incur slippage during backtesting and trading with demo account. Because I was constantly hit with slippage but I understand demo trade and backtesting shouldn’t have slippage… Did any of you incur slippage during backtesting and demo trade too?

*I do use tickstory for the tick data for 99% quality…

Hi, good to have you!