It's not a bug, but anyway...
When I try to get the ClassName of the CoronaPhysicalMtl, I get a returned strange string: "\rCoronaPhysicalMtl"
With line breaks :) This is not a problem, strings can be filtered.
My test pseudocode (MaxSdk .Net API):
IMtlBase matBase.ClassName // MaxSDK pre 2022
IMtlBase matBase.ClassName(false) // MaxSDK 2022 and up