I’ve pushed a fix here, pending review:
https://github.com/ArduPilot/ardupilot/pull/6011
and a prebuilt firmware for you to try here:
http://uav.tridgell.net/tmp/plane-fmuv2-alt-rate-fix.px4
again, thanks for reporting this, its an important fix! Servos could have burnt out in flight causing a crash