No, guys, the synchro blocker ring won't cause one to pop out of gear. The collar that engages the input gear, and the gear itself are worn, and will have to be replaced. A synchronizer assembly consists of the hub, the outer collar, and the blocker rings, and it should be replaced as a unit if possible. The notched teeth on the back of the input shaft, and the synchronizer collar mesh to transmit power in high gear, and one or both of them with chips or wear is the cause of the transmission jumping out of gear.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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