Having problem with Magic Mouse and MBPro Retina 13" 2015

mouse keeps disconnecting - but then reconnects after a few seconds - I also have a 2014 version of the same laptop with no issues - bot are using wireless KB and Magic mouse - batteries are new and they sit next to each other on my desk - each connected to large monitor - one is 27" apple display other (new one ) is Dell 27" 4K monitor