There really is no reason to remove the plastic insert when cleaning the lens. It exposes the delicate electronic circuit board and connectors. My guess is that you may have damaged some of those electronics.
Unless you can see if you dislodged anything or let it alone for a long enough to see if it dries out, the cost of shipping alone will probably be more than a used 50mm f1.8 is worth to repair.
What were you doing, what conditions you were shooting in that required you to do a "deep cleaning" of your lens?
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