<<< after a click on the keyboard/mouse it goes straight to low. >>>
Are you plugging a "wireless" mouse and keyboard into the laptop? Either of these could cause a problem.
When upstairs, is there a "cordless" phone close to the laptop? These are among the worst offenders for interfering with wireless networks.
Close proximity to a central heating radiator can also cause wireless signal problems.
...I even came across a case where the wall cavities of a modern house were lined with aluminium foil for thermal insulation and that just killed any signals outside the room with the router!