System.InvalidOperationException: ValueFactory attempted to access the Value property of this instance.

[Alireza2125]

nswag in system,text,json mode is not thread safety!
because in constructor of generated source use
_settings = new System.Lazy<System.Text.Json.JsonSerializerOptions>(CreateSerializerSettings);
instead of
_settings = new System.Lazy<System.Text.Json.JsonSerializerOptions>(CreateSerializerSettings, true);

[jilles-sg]

According to the documentation (for example https://learn.microsoft.com/en-us/dotnet/api/system.lazy-1?view=net-6.0 ), thread safety is the default. It seems more likely that the implementation of the partial method UpdateJsonSerializerSettings accesses the settings object via the JsonSerializerSettings or similar property instead of via its parameter, as suggested by the exception message.