When you dragged the effect , which timing grid was active
- ie in the small circle on the left hand side - u can have one or multiple "selected"
xl however will only use one active one .
Without going into too many details here , I would guess that when u dropped the effect, there was no timing grid active but u could still see vertical lines.
or what was active was the default timing grid , but u added all the marks to the bars one which then was not the active one when u dropped the effect