You have to read the manual and observe whether the game follows the manual or not. If it follows the manual, it's safe. Once you insert a token on all safe cabinets that follow the manual, the door opens to the next room. (You can read the 'How to Play' in the description)
The games that are safe and are corrupted are different every time so you really have to observe.
Also, ye, the delay of inserting tokens is a known bug from playtesters, will check the code and fix it soon. For now, just keep clicking 'T'
Thank you so much for playing