While looking at TMSX medm screen, I realized that huge AC values were sent to the dac due to damping.
It seems like the damping was not in its right state because the input osem calibration filters were not engaged.
The picture below describes what filters to engage for the damping to be working : There's a "to_um" to engage at the osem bank, and a "from_um" at the damping bank to compensate for the first one. It won't work if only one of them is engaged.