Well, thread title says it:

i am trying to cancel an order but the system don't let me do it, plus price is swinging a lot and i can't understand a thing.. it is a very mess right now, all because of this bitcoincash pump and dump

any other experienced the same? i don't know if the system has already take my actions in account and they are going to be executed anyway or not ...

terrible terrible situation..
I know programming. Programming a trading engine is as simple as ABC, just simple accounting. An honest implementation (which it should be) is to allow immediate cancellation of order. This is very easy to accomplish.

You match orders from a pool of buyers and seller sequentially. Orders to cancel is monitored at another thread. As long as an order is not the orders in the current price matching - and order cancellation should be immediate. Our current processors are very powerful and there is not need to delay any order cancellation.

They lock your order in order to do sure-win arbitrage when they need time to confirm their arbitrage order.

I think there are a few complains about Kraken. Don't trust them.