One possiblility could have occurred while reinstalling the trigger mechanism
Being as you say you have not installed the "Retainer" then can it be assumed you have Not installed the scope mount rail as well. being that the retainer is installed prior to installing the scope mount rail.
Therefore ! could you have already installed the scope rail mounting SCREWS either to prevent from misplacing them or by mistake while reassembling.
This could if done by accident without the scope rail mount installed could result in tightening the screws all the way in which can and could prevent the trigger claws from activating properly. Even one screw if installed can be one too many,
" No scope rail mount in place hence the screws can now penetrate deeper into the trigger compartment contacting the claws and safety mechanism area
I see also from one of your previous posts you have a ADF SCOPE RAIL as well.
Or
Worse case scenario could be your problem is Excalibur in a rush trying to do quick turn around for you did not make proper repairs to your trigger or thought they replaced the one you sent with a new one and by mistake

in a double switch returned your defective one to you instead

..
" Reviewed your Original Trigger Issue Thread which you posted a while ago - it was that you could not get the trigger claws to latch when cocking. So you then returned it for warranty repair or replacement."
CC