2 things to check:-
1. go to unraid docker web ui, left click sonarr and select 'edit' then top right click on 'basic view' toggle to turn it on to 'advanced view', then check the 'repository' it should be set to 'binhex/arch-sonarr' if it has a colon and then some value then you are hard set to a particular tagged image, remove the colon and the value after it.
2. go to unraid docker web ui, click on top right click on 'basic view' toggle to turn it on to 'advanced view' then click on 'force update' link.
this should sort you out, and to answer your question, no i would not expect an old CA plugin to block updates to docker images.