It sounds a lot like classic "foaming". My guess is that the liquids came with some kind of de-foaming agent in them, and after about an hour of use (per your post) the anti-foaming agent evaporated.

Foam can be a challenge to solve, but the most common methods are to search out a de-foaming agent, or add a bubble breaker to the tank.

Take a look at the MSDS sheet for WD 40 and your tapping fluid, and likely it will list the contents, or close enough.