Hello Matt and a very warm welcome to Beoworld.
There can be many reasons for the type of problem you have described.
Firstly, is your AVANT connected to any other products via the Masterlink ? If the answer is Yes, then my first suggested step is to power down the AVANT at the mains plug and remove the Masterlink cable, then power up the AVANT again and review the situation.
How often does this problem occur ?
Let us know what the results of the above questions are...