If you are on version 188.8.131.523 or newer, you should look here:
This article outlines what you can do to collect information about debugging.
When you get an error during export to Excel, you can collect a temporary file that will help our developers determine the reason behind the error. The temporary file is created during the conversion to Excel format. If we get our hands on the file then we can try to reproduce the error on our development system.
The temporary file is located in the folder for temporary files belonging to the service tier process. In a demo installation, the service tier runs under the Network Service user context and the default temporary folder is C:\Windows\ServiceProfiles\NetworkService\AppData\Local\Temp.
If you have a conversion error on your screen, you should be able to find a file with the tmp extension in that folder. There may be many such tmp files but you can use the date to determine which one you should look for. Sort them by date and open the most current in Notepad. It should start with something link this:
PageSettings,2.147484E+09,2.147484E+09,78.74016,78.74016,0,82.67717,False NewDocument NewDocument NewDataItem NewDataItem NewDataItem Control,PageLoop,CopyLoop,Header1,Header,ForNavTextBox1,TextBox,454.7244,0,248.0315,16.65354,"Arial",10,"Bold",4278190080,16777215,Near,Center,True,"Sales - Invoice ",Text
Please zip this file and send it to our support.