I foolishly used only Marbles to defeat my first Golem, after which another Golem did not respawn.
I hit the first Golem with 10 Marbles to defeat the first heart, then 30 Marbles to defeat the second and then 100 Marbles to defeat him completely. I never saw the Golem "fall to the ground", which lead me to assume that I need to continue hitting him with Marbles.
I clearly misunderstood the correlation between the heart colors and the Marbles, Ropes and Buckets of Water.
After defeating him by just using Marbles, I did receive my Quest Reward and, once the group completed the quest, I received my Golden Golem statue.
At the same time I got the reward for defeating the first Golem, I also got the reward for freeing my Home Island of Bandit Camps - which I actually had not done. I never made it a priority to defeat Wild Mary in Sector Nine; all other sectors were cleared and bandit camps were defeated.
After seeing that I received the reward for freeing my Home Island, I sent troops and successfully defeated Wild Mary - there seemed little point in waiting any longer.
All other aspects of game play seem to be working fine, with the exception of a second Golem appearing.
As much as I would enjoy defeating more Golems, it's really no big deal to me - but I figured that I would report for the benefit of other players.