Answer: Though the plant should be hardy enough in your region, it is possible that the outer buds are suffering winter damage anyway. Often, plants that are set on the south side of the house will break dormancy earlier than those set further from the house, because of the reflected heat from the house. The early-forming buds can then be nipped by frost and/or damaged by cold winds. This would explain why the inner branches are flowering--they are more protected than the exposed outer and upper buds. That would be my first guess, and the only solution would be to move the shrub away from the house, or protect it by wrapping with burlap every winter. If you don't want to move it, you can try pruning it back. This should be done soon after flowering; remove older branches to encourage vigorous new ones. You could then try the wrapping technique this fall, and see how the plant fares next spring.
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