I was opening the tubes from the periscope/uzo, and they continued to close themselves, even if i opened them from last to first. Somehow i dint try opening them from the TDC.
I tried opening them on the TDC as you guys suggested, and it worked! this time my tubes stayed open.
It shouldnt be a problem to open them from the tdc. nowadays i enter target data directly into the TDC anyway (no notepad), so i will continue to open them there, right after the last range input.
thanks guys!