Hello I had in all 3 formations there are more than 2 there is one that has disappeared. The defense..

I'm not sure exactly what you mean here but if troops have been removed from the formation then possibly they have been wounded / killed in an attack or perhaps yo have done a promotion / enhancement in the command center that has reset them. Or it may be a glitch. Try reloading the game and reassign the troops as they should be. Check your hospitals as well.

Thank you for your answer. Let's go for the troops I recovered them by improving them.

But in the garrison defense center I do not have the defense formation anymore and so I can not put troops there to defend.

I have that training TPB1 and TPB pro.

Is this a bug?

Same problem gere, did you solve this? I think it's intended, it happened when I leveled to lvl 8.