Please try our latest version/fix: Aspose.Cells for .NET v18.11.3:
Aspose.Cells18.11.3 For .Net2_AuthenticodeSigned.Zip (4.7 MB)
Aspose.Cells18.11.3 For .Net4.0.Zip (4.7 MB)
Aspose.Cells18.11.3 For .NetStandard20.Zip (3.8 MB)
Your issue should be fixed in it.
Let us know your feedback.