i don’t understand the last one, but the cause of the drop is the expiry of t200 timer, which is supervising the layer 2. Basically your radio link was suddenly lost. MS goes indoor, behind a building or something, and the HO couldn’t be done in time.
“reduce load in serving cell”-> it means nothing to me, i do’nt see the connection to the problem, and i’ve never seen that before. Is it a 3GPP lessage ??