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.