Strange Exception when converting Ebook to PDF

Hello,
I try to convert differet document types to PDF.
I have a set of Unit tests. One test converts a Ebook (epub) to PDF.
This test sometime creates an exception. Sometimes the test creates a valid PDF.

The code in the converter:
Aspose.Pdf.EpubLoadOptions option = new Aspose.Pdf.EpubLoadOptions();
using (Aspose.Pdf.Document pdfDocument = new Aspose.Pdf.Document(importFile, option))
pdfDocument.Save(pdfFile);

“Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection’s state is no longer correct.”

at System.Collections.Generic.Dictionary2.FindEntry(TKey key) at System.Collections.Generic.Dictionary2.TryGetValue(TKey key, TValue& value)
at #=zr5zZgS2DErCBBwiXR7yc$KFpNsN1DLxoIw==.#=zp7QWpjw=(#=zAhMtjTb6F$HTOKjf0MXi9Olr7unv #=zm3eKfM0=)
at #=zG8FcYd2kpXy$QcW6ayie_Vo=.#=zFWhYZKg=(#=zzQjZUlEUnC1DC2ctdOwx0Z12_tCM #=ziYoKUeE=)
at #=zIuqYKNfa7K3cvHwC7nJlc8ek3j_l.#=zgz5ISYanbnnn(#=zlNYf3_o= #=zrQ4_mPU=, #=zmhCkt_DS7BaRNG7s0NTY0k4= #=zm3eKfM0=, TimeSpan #=z7rCFPTw=)
at #=zIuqYKNfa7K3cvHwC7nJlc8ek3j_l.#=zxiOiDLQdTmTk(#=zmhCkt_DS7BaRNG7s0NTY0k4= #=zm3eKfM0=, #=zNwEI8GuUBJSvbri8k5cD6X8m1AfV #=zvmWNO_kcxppY, List`1 #=zHC1D0JV68pp5, #=zXDygexd6wom_YG74KCg11NNMpiLP #=zy4ed1OU$Yjk7, TimeSpan #=z7rCFPTw=)
at #=zIuqYKNfa7K3cvHwC7nJlc8ek3j_l.Render(#=zslpV0Tt8mRP$CRg3ujrNdAMjN6gt #=zpjhcTEA=, #=z2fd_48zVg9m2c33lR_tsJfQ= #=zocXPqQQ=, TimeSpan #=z7rCFPTw=, Stream[] #=zHFl$AkM=)
at #=zIuqYKNfa7K3cvHwC7nJlc8ek3j_l.Render(#=zslpV0Tt8mRP$CRg3ujrNdAMjN6gt #=zpjhcTEA=, TimeSpan #=z7rCFPTw=, Stream[] #=zHFl$AkM=)
at #=z8zL_dLnpvvSQQqNmKXOvo64LdgXn.Render(#=zslpV0Tt8mRP$CRg3ujrNdAMjN6gt #=zpjhcTEA=, #=zDX8yB0U= #=zWSWMwpI=, TimeSpan #=z7rCFPTw=)
at #=z8zL_dLnpvvSQQqNmKXOvo64LdgXn.Render(#=zslpV0Tt8mRP$CRg3ujrNdAMjN6gt #=zpjhcTEA=, #=zDX8yB0U= #=zWSWMwpI=)
at #=z92d8U_zjnrfs4FPt9X3EV2NC0FE7.#=zujI9unSjbRsm(Stream #=znzNazr6ervgk5Q2PgQ==, Document #=zkT76WJoewSBY, EpubLoadOptions #=z48c_1lM=)
at Aspose.Pdf.Document.#=z7hSlsVI=(Stream #=zyUEvkTs=, LoadOptions #=z48c_1lM=)
at Aspose.Pdf.Document…ctor(String filename, LoadOptions options)
at SSD.ATLASti.CrossPlatform.AsposeExtensions.SSDEBookToPDFConverter.ConvertToPDF(String importFile, String temp) in C:\Code\Atlas 22 Doc2PDF\Cross Platform\Base Framework\SSD.ATLASti.CrossPlatform.AsposeExtensions\SSDEBookToPDFConverter.cs:line 38

I add the Ebook to the ticketMade_with_Creative_Commons-ePub2.zip (933.9 KB)

@mausbeer

I can not reproduce the issue so I request you to upgrade to latest version and share your feedback.