03 CR125 Zero Compression

Rebuilt my 03 CR125 with OEM A piston, ring and wrist pin, new BR9EG plug and honed cylinder as this was the 1st rebuild on a new A cylinder. Did 3 heat cycles and test road for about 5 minutes. Everything was fine. Life happened and the bike sat without fuel for 6 months after rebuilding.  Added fresh fuel and started bike. After it warmed up, gave about 1/2 throttle to clear it out and it began to bog and then died. It would not restart and immediately I knew it had low compression by the feel of kicker. Pulled plug and it was clean, not fouled. Performed compression test and had maybe 10 psi after 10-15 kicks WOT. Disassembled and inspected. Honda A cylinder measures @ 53.93 -  53.94 at all 4 measurement points. Piston measures in spec and has no damage. Ring is intact but measures at 30 thousandth ring gap which is way to large so this has to be my failure point. .28 is max ring gap according to the manual. What I do not understand is how a new ring that was in spec at time of installation "expanded" to 30 thousandth with no damage to the ring or cylinder walls. Crank and seals have 20 hrs and have zero movement up and down, no engine oil in cylinder and no Premix/gas stator side. Rebuild was performed as maintenance (20 hrs) and bike had good compression before it was rebuilt. I've rebuilt this bike and many other 2 strokes several times over the last 28 years and never experienced this. At a loss. What am I missing?