ASP page error even custom error mode "ON" - asp.net

Question

I've got custom error mode "On" in my web.config. However, the ASPX error page still shows for certain kinds of particular URL
Not OK
https://example.com/*~1*%5ca.aspx <-- Return 404 - File or directory not found.
OK
https://example.com/abc.aspx <-- can redirect to custom page
I'm using Windows Server 2012 Azure. I disabled the NtfsDisable8dot3NameCreation in the registry, but still no luck. What can be the root cause?
My web config
<customErrors mode="On" defaultRedirect="~/error/Error403.html">
<error statusCode="400" redirect="~/error/Error400.html" />
<error statusCode="401" redirect="~/error/Error400.html" />
<error statusCode="402" redirect="~/error/Error400.html" />
<error statusCode="403" redirect="~/error/Error403.html" />
<error statusCode="404" redirect="~/error/Error404.html" />
<error statusCode="500" redirect="~/error/Error500.html" />
<error statusCode="501" redirect="~/error/Error501.html" />
<error statusCode="502" redirect="~/error/Error502.html" />
<error statusCode="503" redirect="~/error/Error503.html" />
<error statusCode="504" redirect="~/error/Error504.html" />
</customErrors>
<httpErrors errorMode="Custom" existingResponse="Auto" defaultResponseMode="ExecuteURL">
<remove statusCode="400" subStatusCode="-1"/>
<remove statusCode="401" subStatusCode="-1"/>
<remove statusCode="402" subStatusCode="-1"/>
<remove statusCode="403" subStatusCode="-1"/>
<remove statusCode="404" subStatusCode="-1"/>
<remove statusCode="500" subStatusCode="-1"/>
<remove statusCode="501" subStatusCode="-1"/>
<remove statusCode="502" subStatusCode="-1"/>
<remove statusCode="503" subStatusCode="-1"/>
<remove statusCode="504" subStatusCode="-1"/>
<!--<error statusCode="500" path="error\InternalServerError.htm"/>
<error statusCode="404" path="error\PageNotFound.htm"/>-->
<error statusCode="400" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error400.html" />
<error statusCode="401" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error400.html" />
<error statusCode="402" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error400.html" />
<error statusCode="403" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error400.html" />
<error statusCode="404" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error404.html" />
<error statusCode="500" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error500.html" />
<error statusCode="501" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error501.html" />
<error statusCode="502" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error502.html" />
<error statusCode="503" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error503.html" />
<error statusCode="504" prefixLanguageFilePath="" responseMode="ExecuteURL" path="/error/Error504.html" />
</httpErrors>

Answer 1

I think you should get 400 error more than 404 error because "*" is not a valid request.path for .NET runtime and the exception was thrown from CLR. That's why IIS custom error page would never work.
Please try to set requestPathInvalidCharacters to null or manual specify invalid characters for your runtime.
<system.web>
<compilation targetFramework="4.8" />
<httpRuntime requestPathInvalidCharacters=""/>
<customErrors mode="RemoteOnly">
<error redirect="https://www.jokiesd.com/404.aspx" statusCode="404" />
</customErrors>
</system.web>
Edit：
I can' reproduce this issue on my 2012 server. Have you tried to replace the URL to abosolute URL?