Exactly as Jonathan puts it. This is a simple problem that for no reason at all sudeenly becomes something that needs special measures like a fien and regular mesh.
Unacceptable.
Even more unacceptable is that it seems to be normal that we, thed usedrs, need to find a workaround for this incorrect answer to a trivial question, while the software owner/ supplier/ maintainer does not seem to be able to come up with a better answer thna: You need a finer/ more regular mesh.
Unacceptable, that why I've given up on PTC as FEAnalysis software provider..