Hexacopter stops at 80m and can't fly over 5.5m/s

I’ve been flying my hexarotor (frame: F550, BLDC motors: dji 2212/920KV, controller board: APM 2.6, tot weight: 1920grs) and I have some doubts about its behaviour.
I’ve attached two graphs with results of some of the missions I did.
Firstly, in the file called height.png I realised that the hexacopter is stopping at 80m height for a few seconds for no apparent reason. I can’t remember configuring that through Mission Planner. Has someone experienced the same attitude? Something similar happens at 12m height and neither can I explain what is happening.
Secondly, in speed.png you can see the average speed of my hexacopter while doing the same missions as in the previous graph. As you can see my multirrotor reaches a climbing speed around 5.5m/s. However, in all three missions I have configured WPNAV_SPEED_UP parameter to be 1000cm/s. At first, I thought I had reached the maximum capacity of my motors, but after checking it, I’ve realised that when ascending, the motors are drawing a total of 45amps from the battery (around 7.5 amps each), which is far from motor absolute maximum ratings. Can anybody help me to understand what might be happening?

I suspect both of these may be bugs that are fixed in 3.2. You really should attach a log file when you’re in the log analysis forum.