Bit raising between depth changes

I am working on a quick practice project. I am using the Harley file to from the Helmet Rack, to make a small plaque.

The cut is working well, but the bit is raising to the safety height in between every depth change. I am cutting to .o6" depth, with a .7mm bit in .015 depth increments. In between each .015 depth change the bit lifts clear.

I have done a few little projects, but this is the first time this has happened. Usually the bit just lowers to the next depth and carries on. Any ideas.