Repair needed for Blackwood Thin Weasel

A problem-

I have a Thin Weasel in Blackwood that dried in storage and the stainless collar and the cedar insert came out. Try as I might I can’t seem to get it back together properly.

Now the whistle plays weak or an octave high. A low G is the lowest pitch that plays with any volume. Thoughts? I loved the whistle prior to this and would like to be able to play it in a session setting but can’t even think about using it missing the bottom three notes and possessing little or no volume. Help! Greatly prefer repair in USA to avoid postage overseas.

All set with a great repairman. Thanks for giving my problem a voice. Cheers, Dave