Version 10.0.0

On a newly upgraded db and with a clean TEMP folder, I get the following after an otherwise clean startup/login and clicking on the first content node.

Some hint on where to start searching for bad data appreciated.

Thanks!

"Index populating failed for populator {Populator}","@l":"Error","@x":"System.InvalidOperationException: Sequence contains more than one matching element\r
   at System.Linq.ThrowHelper.ThrowMoreThanOneMatchException()\r
   at System.Linq.Enumerable.TryGetSingle[TSource](IEnumerable`1 source, Func`2 predicate, Boolean& found)\r
   at Umbraco.Cms.Core.PropertyEditors.PropertyEditorCollection.get_Item(String alias)\r
   at Umbraco.Cms.Infrastructure.Examine.BaseValueSetBuilder`1.AddPropertyValue(IProperty property, String culture, String segment, IDictionary`2 values)\r
   at Umbraco.Cms.Infrastructure.Examine.MediaValueSetBuilder.GetValueSets(IMedia[] media)+MoveNext()\r
   at System.Linq.Lookup`2.Create(IEnumerable`1 source, Func`2 keySelector, IEqualityComparer`1 comparer)\r
   at System.Linq.GroupedEnumerable`2.ToList()\r
   at Umbraco.Cms.Infrastructure.Examine.UmbracoContentIndex.PerformIndexItems(IEnumerable`1 values, Action`1 onComplete)\r
   at Umbraco.Cms.Infrastructure.Examine.MediaIndexPopulator.PopulateIndexes(IReadOnlyList`1 indexes)\r
   at Umbraco.Cms.Infrastructure.Examine.ExamineIndexRebuilder.RebuildIndexes(Boolean onlyEmptyIndexes, TimeSpan delay, CancellationToken cancellationToken)","Populator":"Umbraco.Cms.Infrastructure.Examine.MediaIndexPopulator","SourceContext":"Umbraco.Cms.Infrastructure.Examine.ExamineIndexRebuilder","ProcessId":4328,"ProcessName":"GO2.Umbraco10","ThreadId":18,"ApplicationId":"ef59b8480ab41c4f59f29235b0098bc1f8813ab4","MachineName":"PC34-T15P","Log4NetLevel":"ERROR"}