Underextrusion (by factor 8?) since 17.10.1

[Ricky1975]

I have a UM2 and ran 17.02.1 for a while without any issues. After the update to 17.10.1 or 18.11.1 and a factory reset afterwards, the extrusion from gcode seems to be something like a factor 8 to low.
When I extrude from the printer interface, 100mm result in 100mm filament extruded.
If I reuse an old (and formerly working) gcode, I have to crank up the extrusion multiplier to 800% to get the same result.
If I downgrade to 17.02.1, everything works as usual.

My init code is:
M200 D2.85
G28 ;home all axes
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
[...prime here...]
G92 E0

M501:
Marlin 1.0.0
Last Updated: Nov 17 2018 16:33:14 | Author: Tinker_18.11.1
Free Memory: 2553 PlannerBufferBytes: 1232
Stored settings retrieved
Steps per unit:
M92 X80.08 Y80.14 Z200.02 E294.20
Maximum feedrates (mm/s):
M203 X300.00 Y300.00 Z40.00 E45.00
Maximum Acceleration (mm/s2):
M201 X2000 Y2000 Z30 E5000
Acceleration: S=acceleration, T=retract acceleration
M204 S1000.00 T1000.00
Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s), Z=maximum Z jerk (mm/s), E=maximum E jerk (mm/s)
M205 S0.00 T0.00 B20000 X4.00 Z0.20 E5.00
Home offset (mm):
M206 X0.00 Y0.00 Z-18.90
PID settings:
M301 P17.00 I1.80 D38.00

Is this issue known, or did I do something wrong? I know at least one other guy with a UM2+ who has the same issue.