Buggy Blueprints in Survival; 'too big'

Playing on the Top Hat Naval Survival MP server. It is modded, but even if I remove all modded blocks, the issue persists. What is the issue?


When trying to place a blueprint in Survival, to build it, the Control Block refuses, insisting the blueprint is 'too big'. I talked to the server owner, he said the only limit is that the build must be smaller than one claim area. And yes, the blueprint easily meets this criterion (the screenshot is in a local Creative save, where I was building the blueprint:

Any idea what is going on here?