exosuit

Based on my experience with the game, I would say that this is not a bug and you just need to give it enough time to fill the Atmo Suit.

While normally a duplicant doesn't use all the oxygen in the Atmo Suit and the Atmo Suit Dock usually has 200 kg of O2 in it already, the transfer from the Dock to the Suit is quick. If the Dock doesn't have O2, then the Atmo Suit will continue through the "charging" animation until it has 75 kg of O2.

Since you're oxygen is flowing in at a rate of 500 g/s (1 kg every 2 seconds): 75 kg (s / 0.5 kg) = 150 seconds or 2.5 minutes. Click on the Atmo Suit Dock, and click on the Atmo Suit under Contents. You can see if the Oxygen Tank is less than 75 kg and increasing. Unfortunately you need to exit out of the Atmo Suit selection and re-select it as the number in the description does not dynamically update.

no, because automatically when the suit gets oxygen it is possible to see in the meter that it is gradually disappearing, and as soon as the next oxygen pack arrives the same thing happens until it is empty, it never accumulates and empties itself, just see how it looks like it's disabled and the ones on the side do not have the same effect

Right, the Atmo Suit Dock meter will decrease as the Atmo Suit oxygen tank is filled. Check the oxygen tank of the suit to see if it is moving from zero. If the Atmo Suit Dock has 50 kg (1/4 full of O2), when you add the suit to that dock, it should take all the 50 kg but still need another 25 kg before it becomes available.

Another test would be to wait until the Atmo Suit Dock is completely full, and only then add the Atmo Suit. If that doesn't work, then it's definitely a bug. I'd then suggest posting your save file so that the Devs can pinpoint the source. Thanks!