Rick;
It sounds to me like you became a victim of hydraulics. When you glue a butt cap into the butt end of a reel seat, on some blanks you are trying to displace air built up inside the rod blank. Once you take your finger pressure off the butt cap, it slowly works itself back off, thus air pushing back against the cap ( hydraulics ) and you end up with that 1/8" gap. If it is a metal reel seat, you can apply some heat to the reel seat butt to soften the glue, then scrape it off and reglue it. Next time, try taping the butt cap in place once you have glued it and cleaned the excess glue with rubbing alcohol. You should no longer have any gap.

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