Happens to me too: Latest cura (4.8.0.something), Ultimaker 3 with latest firmware (self updated itself).
Also, it happens every time. Prime blob, then build plate start rising and head starts moving, smashing the prime blob down.
I do not want to disable the prime blob because i had issues without it. Sometimes the extruder got stuck in the beginning and screwed the print. So i find priming the material a must.
As for @upatamby suggestion, i'd go a step further and rather ask the build plate to go down a bit and then rise, because
the prime blob is a bit unpredictable and it would be good to ensure clearance till after the head is gone.
Please add this, it's a nasty bug and it happens all the times.
UM3 is also not a cheap piece of hw, one would expect that such a simple problem would be fixed, given what it costs..