When I open a brush it keeps automatically expanding in size & cursor moves through filmstrip

Cloud Desktop, Windows 10 - Recently when I open brush, the brush size just starts expanding automatically and will not stop.  At the same time when I click an image to open in full view, nothing happens apart form the "cursor" or highlighted filmstrip image starts scrolling through the whole filmstrip???  Microsoft bug checker does not find any virus.  I am using a wireless keyboard & mouse, and will try wired ones when they arrive tomorrow, in case it is something to do with them.  I just updated LR today and the same thing occurs.