OK, given that the code specifically has an assertion to check for this case
already (and this is what failed here), I think we can mark this as resolved then.

Tested this with revision 650:0eaaa80fa3ff.

The assertion fail is caused by a duplicate entry in the effects-vector
(the pair (9,1)).

This pair appears already in the preprocessed output file:
...
takeoff_seg_rww_0_50_north airplane_cfbeg
1
26 0
6
0
32 1 14
0
0 0 1
0
8 -1 0
0
9 -1 1    <- here
0
9 -1 1    <- and here
0
30 -1 1
0
end_operator
...

When using the current translator&preprocessor, this duplicate
disappears - and the problem is solved, even when using the old version
of downward-debug. 
And the current version of downward-debug fails when using the old
translator and preprocessor.

So the fault was in either the preprocessor or the translator, and
apparently disappeared at some time.

The attached problem is solved when using the normal (= release) build, but it
fails an assertion when using downward-debug:

translate.py P03_DOMAIN.PDDL P03_AIRPORT1_P2.PDDL
preprocess < output.sas
downward-debug < output --search 'astar(mas())'

Output of downward-debug:

Simplifying transitions... done!
Conducting best first search with reopening closed nodes, bound = 2147483647
Initializing merge-and-shrink heuristic...
Abstraction size limit: 50000
Abstraction size limit right before merge: 50000
Number of abstractions to maximize over: 1
Merge strategy: linear CG/GOAL, tie breaking on level (main)
Shrink strategy: high f/low h (main)
Label simplification: enabled
Expensive statistics: disabled
Building abstraction nr 0...
Building atomic abstractions...
Building atomic abstractions... unreachable: 0 nodes, irrelevant: 1 nodes
shrink forced: prune unreachable/irrelevant states
done!
Merging abstractions...
next variable: #45
abstraction: 1/46 vars, 2 nodes, ???/4 arcs, 876 bytes
             init h=1, max f=1, max g=1, max h=1 [t=0s]
next variable: #32
unreachable: 0 nodes, irrelevant: 2 nodes
shrink forced: prune unreachable/irrelevant states
abstraction: 2/46 vars, 28 nodes, ???/36 arcs, 1616 bytes
             init h=8, max f=20, max g=20, max h=13 [t=0s]
next variable: #42
downward-debug: operator_registry.cc:32:
OperatorSignature::OperatorSignature(const std::vector<std::pair<int, int>,
std::allocator<std::pair<int, int> > >&, const std::vector<std::pair<int, int>,
std::allocator<std::pair<int, int> > >&): Assertion `effects[i].first >
effects[i - 1].first' failed.
Peak memory: 4176 KB
caught signal 6 -- exiting
Aborted