water source block does not unfreeze until block next to it is mined

We have an iron golem farm which uses water to push golems into lava. After walking past the two water source blocks while wearing frost walker 2 boots, the water source blocks freeze as normal. Upon removal of the frost walker boots, the water source blocks do no unfreeze. After mining a block next to one of the water source blocks, both water source blocks unfreeze, and the iron golem farm becomes functional again.