OwnerOps please note the following:

1) never change status of files in transcoder queue it may lead to unpredictable results

2) check if remote transcoding option isn't enabled Developer > Settings > Remote video transcoding, it requires special setup

2) original issue was related to the problem when some webm files left in queue after webm transcoders were removed in some of previous updates, then clearing transcoding queue should help - https://una.io/cmts.php?sys=bx_forum&id=3869&cmt_id=15645