surface source gives strange result after set up angle distributions

[tontyoutoure]

Describe the bug
The next two images are the result of the .mac script I present below. The only difference is one is generated by Volume type (which gives result I expect) and one is generated by Surface type. I wonder if this is a bug or some undocumented behavior.

• Gate version or commit hash: v9.4

Minimal example
main.mac:

# randoms 

/gate/random/setEngineName MersenneTwister
/gate/random/setEngineSeed auto

# physics list
/gate/physics/addPhysicsList emstandard_opt3

/gate/physics/setDEDXBinning 500
/gate/physics/setLambdaBinning 500



# initialize
/gate/run/initialize


/gate/source/addSource  point_source gps
/gate/source/point_source/gps/particle gamma
/gate/source/point_source/gps/ene/mono 141 keV
/gate/source/point_source/gps/pos/type Surface
#/gate/source/point_source/gps/pos/type Volume
/gate/source/point_source/gps/pos/shape Cylinder
/gate/source/point_source/gps/pos/radius 2 mm
/gate/source/point_source/gps/pos/halfz 2 mm
/gate/source/point_source/gps/pos/centre 0 0 0 mm
/gate/source/point_source/gps/angtype iso
/gate/source/point_source/gps/mintheta 89 deg
/gate/source/point_source/gps/maxtheta 91 deg
/gate/source/point_source/gps/minphi 179 deg
/gate/source/point_source/gps/maxphi 181 deg

/gate/source/point_source/setActivity 100 Bq



#viualization


/vis/open                           OGLSQt 1920x1080-0+0
/vis/viewer/set/viewpointThetaPhi   -90 90 deg
/vis/viewer/zoom                    5
/vis/viewer/set/style w
/vis/drawVolume
/vis/viewer/flush
#/tracking/verbose 0
/tracking/storeTrajectory 1
/vis/scene/add/hits 
/vis/scene/add/trajectories 
/vis/scene/endOfEventAction         accumulate -1
/vis/scene/add/axes 



/gate/output/allowNoOutput

/gate/application/setTimeSlice     1  s
/gate/application/setTimeStart     0.0  s
/gate/application/setTimeStop      1  s

/gate/application/startDAQ