Serializing and deserializing a ArrayList

What changed in 2.1 preview 4 this does not work anymore?

 #### Exception System.NullReferenceException - CLR_E_NULL_REFERENCE (4) ####
    #### Message: 
    #### System.AppDomain::CreateInstanceAndUnwrap [IP: 0013] ####
    #### GHIElectronics.TinyCLR.Data.Json.JsonConverter::DefaultInstanceFactory [IP: 008a] ####
    #### GHIElectronics.TinyCLR.Data.Json.JsonConverter::PopulateObject [IP: 0027] ####
    #### GHIElectronics.TinyCLR.Data.Json.JsonConverter::DeserializeObject [IP: 000c] ####

edit: 6 days ago, there is a mention that enums dont work
Json Deserialized example - TinyCLR OS - GHI Electronics’ Forums
but they worked in TinyCLR 2.0

edit2: tried without enum, only simple int, same error