CoreML : “Unexpected error processing model” error sometimes occurring

Context:
I'm using a custom CoreML model made by a datascientist. The model is a pipeline that uses Apple

SoundAnalysisPreprocessing
model as it's first model.
SoundAnalysisPreprocessing
model is followed by a custom model that contains different convolution layers and a softmax.

Issue:
When launching a prediction, I sometimes get

Unexpected error processing model
. With the exact same input, I sometimes get a correct result and sometimes I get this error.

Question:
I have no clue what to do with this error. Is it a memory problem with input being badly allocated ? Is it a problem with the model itself ? Do you have any idea what I could do to understand what is happening ?

Complete error log:


[DSPGraph] throwing DSPGraph::Exception with backtrace:

0 0x7fff2bcf5df9 DSPGraph::Graph::processMultiple(DSPGraph::GraphIOData*, DSPGraph::GraphIOData*) + 249

1 0x7fff2bc3b570 processThroughGraph(id<MLFeatureProvider>, MLMultiArrayConstraint*, MLMultiArray*, NSString*, DSPGraph::Graph&, std::__1::vector<float, DSPGraph::Graph&::allocator<float> >&, void (DSPGraph::Graph, NSString*::GraphIOData&) block_pointer, NSError* __autoreleasing*) + 979

2 0x7fff2bc3c573 -[SNDSPGraphCustomModel predictionFromFeatures:options:error:] + 195

3 0x7fff2bc3ca49 -[_SNVGGishFrontEndProcessingCustomModel predictionFromFeatures:options:error:] + 98

4 0x7fff2496ac30 -[MLAppleSoundAnalysisPreprocessing predictionFromFeatures:options:error:] + 132

5 0x7fff248d345c -[MLPipeline predictionFromFeatures:options:error:] + 178

6 0x7fff24923f76 -[MLModel predictionFromFeatures:error:] + 92

7 0x104b89a68 $s10TestCoreML17AudioFileAnalyzerC019previsionWithManualD3Cut33_1966162A0510E69792A8D979B37CC177LL3for10completiony10Foundation3URLV_ySo12MLMultiArrayCSgXEtF + 5992

8 0x104b87850 $s10TestCoreML17AudioFileAnalyzerC05startF03for10completiony10Foundation3URLV_yyXEtF + 80

9 0x104bb360c $s10TestCoreML23ClassificationViewModelC14startRecognize4word8mockData11resultBlock06finishM0ySS_SbySb_SaySo16SNClassificationCGSgtcSgyyctF + 3436

10 0x104bad21c $s10TestCoreML18ReadViewControllerC010collectionE0_15didSelectItemAtySo012UICollectionE0C_10Foundation9IndexPathVtFyycfU_ + 220

11 0x104b923fd $sIeg_IeyB_TR + 45

12 0x104f79d64 _dispatch_client_callout + 8

13 0x104f7c6d6 _dispatch_continuation_pop + 552

14 0x104f8fa8f _dispatch_source_invoke + 2205

15 0x104f87c53 _dispatch_main_queue_callback_4CF + 1043

[truncated?]

2019-10-30 20:33:04.209693+0100 TestCoreML[5024:191792] [] Caught graph exception 1718775073 !mrf fromBytePos (0) + numBytesToCopy (61440) > mABL->mBuffers[0].mDataByteSize (2112) in /BuildRoot/Library/Caches/com.apple.xbs/Sources/Listen_Sim/Listen-35/CoreAudioUtility/Source/CADSP/DSPGraph/DSPGraph_Utils.cpp:742