Brand new tap timer leaks around collar plumbing advice

Brand new tap timer leaks around collar Per the pics attached, I have a brand new tap timer fitted to my outdoor tap with a brand new washer. It always leaks from the bottom of the fitting collar. I have tried four different washers (all pictured), both individually and in combination. I have tried tightening the connection, loosening the connection, applying lots of PTFE-tape, applying a little PTFE-tape, applying no-PTFE tape.. always the same leak. Any suggestions? Most online advice relates the the washers: should I try to source a different type of washer perhaps?

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