Nakajima Homare: great design or trouble source?

I guess that Japanese Homare engine is a well known historical item to the fellow members.
On the modest displacement, weight size, it was managing to provide decent power. Both down low and at higher altitudes. However, the reliability issues were present during it's service history. What I'm interested about is whether those issues were inherent to the design, or were a consequence of problematical Japanese situation re. fuel material/metal quality? Maybe a combination of more issues, or things that were done wrong during project, production and/or maintenance phases? Perhaps they should tried with fan cooler?

My guess is the second option (declining workmanship and maintenance standards) but I'm far from an expert.

IIRC one main reason was very strictly enforced conscription by Army, it combed very thoroughly also skilled factory workforce for new drafteers and before replacements were fully trained they were drafted too.

Juha