Caused by18b693bdbd, due to lack of thread safety. Beteween calling BKE_sequencer_cache_get_num_items and BKE_sequencer_cache_iterate New items could be inserted in the cache. BKE_sequencer_cache_iterate() now use 2 callbcack functions for initial setup during which buffers with correct length can be initialized and finally iterating. Additionally drawing of unselected items was fixed again introduced in18b693bdbd. T74662 is reporting quite different symptoms, than I get on my machine, so I am not entirely sure this is complete fix. Reviewed By: brecht Differential Revision: https://developer.blender.org/D7220