Addin randomly crashing Excel

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Addin randomly crashing Excel
Excel crashing unexpectedly with addin installed 
Sean Devenish

Posts: 75
Joined: 2015-11-30

We have a number of clients reporting Excel crashing while using our addin.
The crashing occurs unexpectedly and has not been linked to any activity in particular. Below is the error log from event viewer identifying the module mso40uiwin32client.dll to be faulting. This appears to be common with all our crashing events.

Log Name:      Application
Source:        Application Error
Date:          04/08/2020 12:48:59 PM
Event ID:      1000
Task Category: (100)
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      N/A
Faulting application name: EXCEL.EXE, version: 16.0.12527.20612, time stamp: 0x5eb49991
Faulting module name: mso40uiwin32client.dll, version:, time stamp: 0x5eb494b4
Exception code: 0xc0000005
Fault offset: 0x0014dfd5
Faulting process id: 0x3670
Faulting application start time: 0x01d66a065db69d1c
Faulting application path: C:Program Files (x86)Microsoft OfficeRootOffice16EXCEL.EXE
Faulting module path: C:Program Files (x86)Common FilesMicrosoft SharedOffice16mso40uiwin32client.dll
Report Id: 2ff0c7d2-c34d-40b1-a6cc-ecd5123b4f85
Faulting package full name: 
Faulting package-relative application ID: 
Event Xml:
<Event xmlns="">
    <Provider Name="Application Error" />
    <EventID Qualifiers="0">1000</EventID>
    <TimeCreated SystemTime="2020-08-04T02:48:59.020441400Z" />
    <Security />
    <Data>C:Program Files (x86)Microsoft OfficeRootOffice16EXCEL.EXE</Data>
    <Data>C:Program Files (x86)Common FilesMicrosoft SharedOffice16mso40uiwin32client.dll</Data>

We have not been able to identify any other related issues from our logs.
Are you aware of this module causing issues? Any help would be greatly appreciated.
Posted 04 Nov, 2020 18:28:26 Top
Andrei Smolin

Add-in Express team

Posts: 17493
Joined: 2006-05-11
Hello Sean,

Open File | Account, see the area to the right of the "About Excel" button. Please provide:
- version
- build
- is it "Click=to-Run"?
- channel

We have a number of Office versions installed and we test our end-user add-ins on them. I'll check if we got such issues.

Did you get it with other add-ins disabled? Do you get it on an empty add-in showing the UI similar to the UI of your real add-in?

Regards from Belarus (GMT+3),

Andrei Smolin
Add-in Express Team Leader
Posted 05 Nov, 2020 03:27:47 Top
Sean Devenish

Posts: 75
Joined: 2015-11-30
Hi Andrei,

We are working with affected clients to get more details to you, as of now we know one affected version of Office is Microsoft Excel for Office 365 MSO (16.0.12527.21230) 32-bit.

With our initial testing other add-ins were disabled when it occurred. It appears to occur randomly and as such have not been able to reliably replicate it.

Will provide more info as it becomes available.

Posted 09 Nov, 2020 22:57:11 Top