Alan racing frame - should I repair?

[latman]

Alan frames definitely glued AND screwed. There's a entry somewhere on the site that I posted of a leaflet explaining it. The seat tube was the last one fitted which screws into the BB shell but just 'passes through' the seat cluster as this is the only joint that can't be screwed if you think about it.

Sequence is probably -

Head tube into top and bottom lugs
Top tube into top lug
Down tube into bottom lug
BB shell onto down tube
Seat cluster onto top tube
Seat tube through seat cluster into BB shell
Seat and Chainstays then added.

How to get the Down Tube loose enough to re-glue it without straining other joints is probably the worst problem - but how does it come loose in the first place?

I fitted a 40mm carbon OD Downtube over an internal lug in an early Peugeot frame and i'm sure it would be LOTS stiffer than this skinny tubed alloy frame .
Maybe the continual road shock was able to break the old glue bonds ? surely the only way for it to move a lot is to follow the threading but it may be really noisy if the glue has let go. Maybe the threading is very shallow"female" on the tubings walls and the respective shallow "male" on the lugs inside ? anyone know ?