It seems you are not alone. It could be an issue with the on-set buttons failing. See below.
https://www.avforums.com/threads/bush-lt26m1ca-sound-osd-issue.1276217/
(But the above solution is a bit extreme. Far better to get an electronics competent friend to see if they can simply disconect or repair the buttons :-) )
http://www.fixya.com/support/t13443322-bush_lt26m1ca_random_menu_changes
X, February 2015