Hi!

We just upgraded to 12.17.1 and after that our properties of the type IList<ContenteReference> is not rendered properly.

I get this error message:

Unable to load /EPiServer/cms/Stores/contentstructure/ status: 500
SyntaxError: Unexpected token '<'
    at dojo.fromJson (dojo.js:15:82234)
    at Object.json (dojo.js:15:120242)
    at _497 (dojo.js:15:123066)
    at _2cd (dojo.js:15:73012)
    at _2cb (dojo.js:15:72704)
    at resolve.callback (dojo.js:15:73525)
    at dojo.js:15:125114
    at _2f2 (dojo.js:15:75368)
    at _2ec (dojo.js:15:75232)
    at _2f1.resolve (dojo.js:15:76693)

System.ArgumentNullException: Value cannot be null. (Parameter 'contentLink')
   at EPiServer.Core.Internal.ContentInstanceCache.GetCacheKey(ContentReference contentLink, String language)
   at EPiServer.Core.Internal.ContentInstanceCache.TryGet(ContentReference contentLink, String language, IContent& instance)
   at EPiServer.Core.ContentProvider.GetScatteredContents(IEnumerable`1 contentLinks, ILanguageSelector selector)
   at EPiServer.Core.Internal.ProviderPipelineImplementation.GetItems(ContentProvider provider, IList`1 contentLinks, LoaderOptions loaderOptions)
   at EPiServer.Core.Internal.DefaultContentLoader.GetItems(IEnumerable`1 contentLinks, LoaderOptions loaderOptions)
   at EPiServer.Core.Internal.DefaultContentRepository.GetItems(IEnumerable`1 contentLinks, LoaderOptions settings)
   at EPiServer.Cms.Shell.Service.Internal.ContentLoaderService.GetItems(IEnumerable`1 contentReferences, LoaderOptions loaderOptions)
   at EPiServer.Cms.Shell.UI.Rest.Internal.ContentStore.List(IEnumerable`1 ids)
   at lambda_method2622(Closure , Object , Object[] )
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.SyncActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeActionMethodAsync()
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeNextActionFilterAsync()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authorization.Policy.AuthorizationMiddlewareResultHandler.HandleAsync(RequestDelegate next, HttpContext context, AuthorizationPolicy policy, PolicyAuthorizationResult authorizeResult)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.ResponseCaching.ResponseCachingMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Localization.RequestLocalizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.StatusCodePagesMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

{
    "url": "/EPiServer/cms/Stores/contentstructure/",
    "headers": {
        "Accept": "application/javascript, application/json",
        "Content-Type": "application/json",
        "X-Http-Method-Override": "List",
        "RequestVerificationToken": "CfDJ8EG1TFyXU-lFgyXJyxqjaciGYcnHMVZUMp5aTY-XMqC0vl930gA7w20NqUytqrTy_l2-3AT4QnBG29H4vw6spEKX33v8PRG7CCfdfglnco-JGAuXdzzAFRjMizKTxlfFzo4ROsNsBvDvPQIFjRpoTuBYgbj6K9y9RogC7JU-gO_IEAxBBhas00F4mInlOFeGfQ",
        "X-EPiCurrentContentContext": "252565_756054",
        "X-EPiContentLanguage": "sv"
    },
    "postData": "[\"43658\",\"44775\",\"257806\",\"38058\",\"38017\",\"280207\",\"41828\",\"\",\"38870\"]",
    "handleAs": "json"
}
}

Some properties of that type is actually rendered correctly so it might have something with the data stored?
The page with the invalid property renders correctly when I view it so there is data stored in the database. Also adding removing references programaticlly works fine, the property is updated and not other data is lost.

Data in the database is stored like this:

["e27309f5-0e90-46dc-bc6d-5e5e200d96ef","daf5c87a-662b-4ee4-9eb2-4a93dc7c4689","1ef05eb0-a6e2-4ba9-ba5d-a170827d34a9","8170c16d-0cff-4ad9-8f3c-247b4c5294ef","8ff2a7f3-ed09-4302-98c4-7097ee93983f","e6d6d915-7c2f-4c10-ab50-c04d7d535006","80e42179-c784-4ef1-8740-524cfd5b7a66","ef2cba23-0d59-4ea2-adba-71c4b1d2cc16","f15b07e7-9ebd-4873-b510-fce3cf03a1b1"]

It is nine links rendered is only eight so could it be that one of the links is invalid and that the edit mode cannot handle that? And in the "postData" it looks like one of the links are empty.

Not sure where to start here. 

Thanks!

/Kristoffer