During work I found following logs in event viewer:
Exception information: Exception type: CrmException Exception message: Could not find a web resource with name Images/refresh.png. at Microsoft.Crm.Application.Components.Handlers.WebResource.RetrieveWebResource(String webResourceName, String preview) at Microsoft.Crm.Application.Components.Handlers.WebResource.ProcessRequestInternal(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
I rechecked existing customization and the only Images/refresh.png was an image that was imported into the system with Activity Feeds solution. I rechecked all html and js webresources of Activity Feed Solution and I found 2 suspicious constructions in scripts:
Error was obvious – ../ was wrong part of reference to image. And solution was obvious as well. I extracted all solution component from solution, found js webresource with errors (msdyn_ActivityFeedsMentionsjsdcd634d6-1470-4b8f-8e19-89849fa559ba and msdyn_ActivityFeedsUIjs619c6362-849a-4c96-bf6f-341444117795), fixed error and archived solution back, imported to the system and error disappeared.