So, does this mean you get scammed in the past, or are you using a terrible platform right now that occasionally has this system glitch you're talking about? If they are new, have no past records, or even have accusations about locking/blocking withdrawal from users, then I also believe you need to leave them asap. If you did get scammed by similar tactics in the past, I think it should be easy for you to do this.
How do we easily take away our investment it crashes?
You can't take your deposited money back when they stop their system. Even if you are not on a scammer platform, you still can't do it, hence why you need to have some degree of trust when using a centralized platform. If you don't want to do that, use a decentralized platform.
What's your best advise to this view?
What do we do when such incident occurs in our trading platform's?
IMO, If you must use a centralized platform, only send the money you can afford to lose. When more reliable decentralized alternatives appear, consider moving there. If you just want to trade occasionally just stop using a centralized platform and move to dex. No need to risk your money, privacy, and security just to get some flexibility.