{@inheritDoc} doesn't support multiple levels of inheritage

[DerManoMann]

If a method/class is overwritten/extended multiple times with both sublalsses using {@inheritdoc}, the tag is not resolved.
Instead, the {@inheritdoc} of the respective parent class is used.

The code would need to go up the class hierarchy until it finds the first non {@inheritdoc} documentation block.

[dbu]

another non-working case is:
class A with method a
class B extends A but does not overwrite method a
class C extends B and overwrites method a, uses {@inheritdoc}

the doc of method a in class C is just empty.