One way is get the Brownells detent drill.It s a long drill that slips through the plunger tube..You can use a pin chuck or fashion a handle and just turn it by hand.No motor necessary.Or,after you fit it,you can just work it,see the shiny line the plunger makes.
That's not necessarily a recommendation.
I've only done four or five of them,I'm not a 1911 ghuru,but of the safeties I've used,none had that issue.
I don't know who made yours,but you might call them.Ask.Sometimes a production part gets a missed operation.Dang dope heads!
It also might just be an angled surface bearing on the plunger.
On a Colt safety,there is a slight detent for "Safety Off"
but for "safety on" its just the contour of the flat plate of the safety body.Its a flat cam.When dropping the safety off,the plunger just goes around a corner.
Off topic to the slide stop..premium slide stops are expensive.I lost a couple to playing the detent game before I figured out a subtle slope with a plunger against it works fine.Remember the mag follower/spring on an empty mag has to be strong enough to overcome whatever "detent" is created. At least,if you want the slide to stay open last round.
I've found second guessing JMB is expensive.So is modding a 1911 part before I completely understand the subtle genius JMB put in it.(which applies directly to Dremel tools!)But,gollygosh,a guy sure learns along the way!!
Fit the safety,see how it works first.