I'm updating the project from 7.7.13 to 7.15.3. First, I run the Umbraco upgrade to 7.15.3 and the I run the migrations that will do the necessary changes on doc. types, data types etc.

The problem is that migration takes too long (like 10-15 minutes on SSD) and the cause seems to be this Newtonsoft.Json.JsonReaderException.

For example, I come to the part in migration where I want to Empty the content recycle bin from code and it first throws this exception 100 times before it actually does the cleaning of RB. Same thing occurs several more times during migration (whole 3 minutes just this exception) and I can't trace it, probably it occurs when I do some actions in db but I can't say whats the reason. Could it be something with Tag property? It occures on Umbraco.Core.Services.TagExtractor.SetPropertyTags() method.

Can someone with more internal knowledge tell me more about this exception and how can I prevent it from occuring?

    2019-12-06 15:24:10,962 [P49420/D12/T21] WARN  Umbraco.Core.Services.TagExtractor - Could not automatically convert stored json value to an enumerable string. Exception: Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: m. Path '', line 0, position 0.
   at Newtonsoft.Json.JsonTextReader.ParseValue()
   at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
   at Umbraco.Core.Services.TagExtractor.SetPropertyTags(Property property, Object convertedPropertyValue, String delimiter, Boolean replaceTags, String tagGroup, TagValueType valueType, TagCacheStorageType storageType)
 2019-12-06 15:24:10,963 [P49420/D12/T21] WARN  Umbraco.Core.Services.TagExtractor - Could not automatically convert stored json value to an enumerable string. Exception: Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: m. Path '', line 0, position 0.
   at Newtonsoft.Json.JsonTextReader.ParseValue()
   at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
   at Umbraco.Core.Services.TagExtractor.SetPropertyTags(Property property, Object convertedPropertyValue, String delimiter, Boolean replaceTags, String tagGroup, TagValueType valueType, TagCacheStorageType storageType)
 2019-12-06 15:24:10,964 [P49420/D12/T21] WARN  Umbraco.Core.Services.TagExtractor - Could not automatically convert stored json value to an enumerable string. Exception: Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: e. Path '', line 0, position 0.
   at Newtonsoft.Json.JsonTextReader.ParseValue()
   at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
   at Umbraco.Core.Services.TagExtractor.SetPropertyTags(Property property, Object convertedPropertyValue, String delimiter, Boolean replaceTags, String tagGroup, TagValueType valueType, TagCacheStorageType storageType)