CollimatorPhysics: Error{0}> reduce: mismatched element count in vector reduction.

Summary

When running the Degrader-1 test OPAL prints the error message 'Error{0}> reduce: mismatched element count in vector reduction.' and then stops working.

Steps to reproduce

Run the Degrader-1 test in parallel.

What is the current bug behavior?

It stops working. It looks like a deadlock.

What is the expected correct behavior?

It should run smoothly to the end of the lattice.

Relevant logs and/or screenshots

ParallelTTracker {0}[3]> 23:33:54 Step    145 at 21.219 [mm], t= 191.015 [ps], E=72.000 [MeV]
ParallelTTracker {0}[2]> --- CollimatorPhysics - Name DEG1 Material GRAPHITE
ParallelTTracker {0}[2]> Particle Statistics @ 23:33:55
ParallelTTracker {0}[2]>             entered: 4'343
ParallelTTracker {0}[2]>          rediffused: 0
ParallelTTracker {0}[2]>             stopped: 0
ParallelTTracker {0}[2]>   total in material: 996'243
ParallelTTracker {0}[3]> 23:33:55 Step    146 at 21.328 [mm], t= 192.015 [ps], E=72.000 [MeV]
ParallelTTracker {0}[2]> --- CollimatorPhysics - Name DEG1 Material GRAPHITE
ParallelTTracker {0}[2]> Particle Statistics @ 23:33:55
ParallelTTracker {0}[2]>             entered: 2'480
ParallelTTracker {0}[2]>          rediffused: 0
ParallelTTracker {0}[2]>             stopped: 0
ParallelTTracker {0}[2]>   total in material: 998'723
ParallelTTracker {0}[3]> 23:33:55 Step    147 at 21.438 [mm], t= 193.015 [ps], E=72.000 [MeV]
ParallelTTracker {0}[2]> --- CollimatorPhysics - Name DEG1 Material GRAPHITE
ParallelTTracker {0}[2]> Particle Statistics @ 23:33:56
ParallelTTracker {0}[2]>             entered: 1'277
ParallelTTracker {0}[2]>          rediffused: 0
ParallelTTracker {0}[2]>             stopped: 0
ParallelTTracker {0}[2]>   total in material: 1000'000
ParallelTTracker {0}> All particles in degrader
Error{0}> reduce: mismatched element count in vector reduction.