The oscillo trace show you exactly what is suppose to happen with any mechanical push-button.

theory and explanation bellow
http://www.elexp.com/t_bounc.htm

Solution... there's many different. Using PBP BUTTON command, use Timers interrupts, OR use a simple loop

Code:
PushButtonA VAR PORTA.0
'
'
'
'
IF PORTA.0=1 THEN
    ' Do your Stuff
    '
    WHILE PORTA.0=1 : Wend ' wait untill push button is release
    PAUSE 50 ' Debounce delay
    ENDIF