It depends on broker. Demo should not suffer from requotes, delays or other issues.
Trading with good real broker should not as well.
On the other hand recently I faced sllipage of 50,000 ms on FxPro and they are not able to explain it .
I think when trading with a good broker slippage is market-related fact, for example. I am afraid it is not possible for it to be replicated on demo, thus there is still a difference even with good brokers.
You mean your order was delayed by 50 seconds? If so, what was your actual slippage in pips? If they are B-Booking, they don't want to explain it for sure 😄