JVC RX-552V A/V Receiver now cares where I stand

[Maplewood_Ken]

This receiver, purchased second-hand, has given good service for a number of years.  However, when listening to music on FM radio, it now matters where I stand or sit in the room, which it formerly did not do.  Depending on my location, the sound is great, or the sound has strong fuzz overlaid.  I am sure there is a term for this phenomenon, but unfortunately I do not know what it is and my searches based on guessing were not productive.

An education on terminology would be a help, and ideas about ways to fix this that do not involve my donning a tinfoil hat would be very much appreciated.   

Thank you for reading.

[Haenk]

I don't know how old you are, but there we're comic strips dating to the 50s - family is sitting in front of a TV, dad is fiddling with the antenna.
That issue still persists. You need to better direct your antenna, get an external antenna (on the roof) or depending on the age of the receiver, change the frequeny by a bit.
I assume this is an issue of waves reflecting uncontrollable within your room.
Back then, the best fix hast been a roof antenna, or coax cable, If available.