Problem with Trailing Stop

I had a working order with active Trailing Stop. Altough the profit in points was even higher than TS level the Trailing Stop didn't work. The terminal was on all the time. In log file from that day there where messages:

modification of order #..... failed [Trade context is busy]

or

modification of order #..... failed [Invalid S/L or T/S].

Can you please explain why TS did not work?

Thank you

A.