docs(troubleshooting): cannot find system.text.json after deploy

Author: marin-bratanov

troubleshooting/deployment.md

@@ -81,6 +81,8 @@ At the time of writing, sometimes the following issues have been reported that p
 
 * `Trial Message` - if the machine that performs the build has access to a trial version of our NuGet package, the framework may get confused and copy a trial assembly to the publish location and you may see the trial messages live. Solutions are available in the [Upgrade Troubleshooting - I Still See the Trial Message]({%slug upgrade-tutorial%}#i-still-see-the-trial-message) article.
 
+* `Could not load file or assembly 'System.Text.Json, ...` - Sometimes this exception is thrown in production (when you deploy the app to another server) when you use things like charts, tooltips or other code that relies on serialization. The usual problem is that the server is missing the corresponding .NET Core version the app was built with. Some reports also indicate that adding explicitly the `System.Text.Json` package to the Blazor project solves problem.
+
 We have also had reports that hosting a Server-side Blazor app on a cloud service, or even on a server that is relatively remote to the client, causes issues. The network latency may interrupt, break or re-arrange the SignalR packets and this can cause a variety of usability issues - from sluggish responses to wrong UI elements responding, or errors. If your users will have a large latency to the server, you may want to consider the Client-side (WASM) model or at least test what the experience is before rolling out to production.
 
 * In Azure, for example, WebSockets are disabled by default, and this is detrimental to the performance of the SignalR connection. Enabling WebSockets may help you get the needed speed and responsiveness from the server.