Okay ~ Listen carefully as I shall say this only once.
Many of the problems with the PM facility are being caused by people not using the correct name for the recipient. This has been the case since everyone started using additional names.
The PM system is case sensitive and also works only if you use the other person's user name as originally entered by them. These can be found by using the members list but often the click on PM facility under their avatar does not recognise the new name such as "Marley's Ghost (Imbiber of Spirits)"
This also applies to the answer facility as their PM to you does show the additional bits and the PM system doesn't recognise it.
Gorrit?