Trying to replicate more like YOUR script does (runs in the background) ... have a theory that maybe "other windows" are "interfering" with show/hide and enablement. This script runs by itself:

just as a test, might want to try running BBChecker all by itself (no apps or windows open) ... does it still hang ?

code:
break on
 
$form = createobject("kixtart.form")
$form.caption = mainform
$form.fontname = verdana
$form.fontsize = 12
 
$button = $form.commandbutton("just a button")
$button.center
 
$form.center
$form.show

$DELAY = 4000 ; msecs
$timer = @TICKS+$delay

while $form.visible
 
 $=execute($form.doevents(1))
 
 if @TICKS > $timer
  $form.hide
  pop()
  $form.show
  $timer = @TICKS+$delay
 endif
 
 sleep(0.01)
  
loop
 
exit 1
 
function pop
 
 dim $popup,$timer
  
 $popup = createobject("kixtart.form")
 
 $popup.caption = popup
 $popup.witdh = 200
 $popup.height = 200
 
 $popup.center
 $popup.show
 
 $timer = @TICKS+$delay
 
 while $popup.visible
 
  $=execute($popup.doevents(1))
 
  if @TICKS > $timer
   $popup.hide
  endif
 
  sleep(0.01)
 
 loop
 
endfunction