Puff,
Headset type makes utterly no difference of course. I am sure u would love a senheiser on your head, but there's just no technical reason for it.
Possible causes of "echoing" could be multipath signals arriving at the receiver out of phase, or an audio problem with the aircraft's audio system.
I am sure it will be reported and fixed in due course if it is an audio system problem.
No, the pilots may not be aware of it depending on what unit the sidetone is generated in.