I have seen Nifti do nasty damage to inserts and raise them and fog them.
Another pin restorer up in Qld was using it & had problems with it.

IF u get all of it off it's not an issue but if it runs into a insert it can be a big problem.

Best product I clean my 50 something playfields with are Baby Bum Wipes.
Why ? They can clean the nastiest shit off and never hurt a delicate baby's skin so I know it will never hurt my playfields. Lol
Also, when the baby wipe stops turning anything other than stark white, you know the playfield n any hardware is now very clean. Sometimes simple for cleaning is best.
After using Mills Wax and the other brands of polish, I always use the baby bum wipes to get any left over polish residues because those polishes are full of petro chemicals.
They can't be good for plastic or wood regardless of what people think or what the bottle says.
Just my opinion but I find best to be safe than sorry. Playfields are too fragile to risk.
Hope the baby bum wipes help anyone who is interested.