Please understand it is hard for us to provide suggestion on specific registry key from RDS perspective. If you could like to test the deleting registry key, it is always suggested to do this on the test VM and backup important data.
I just searched a while and found that there were different versions of the codec but all named l3codecb.acm. Not sure if it is related the compatibility of windows versions.
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Hope this helps and please help to accept as Answer if the response is useful.