Valve sputtering noise when refilling

Installed a Toto Drake about a month ago and everything was fine.

Both I and my wife noticed two days ago that the sound that the toilet makes when refilling after the flush is noisier all of a sudden.

The sound has changed from a smooth steady refill sound, to a refill sound that is uneven and includes intermittent sputtering or tapping/bubbling sounds.

It's very noticeable and seems to be coming from the G-max flush valve unit only when the toilet is refilling.

Anyone have any idea what this could be or if it is an easy thing to remedy?

Contact the place of purchase if you did the install or the plumber if sh/e supplied and installed the toilet for you.
It could be as simple as taking the fill valve apart & cleaning it or just installing a new one.

A. Turn off water supply. Flush toilet. Remove refill tube and snap off cover (A)

B. Remove float by gently squeezing float arms inward. (B)

C. While holding valve with one hand, twist cap 1/8 turn counter-clockwise and remove. (C)

D. Lift out center tube. (D)

E. Use pliers to remove strainer from center tube. (E) Clean strainer and cap by rinsing under running water.

F. Re-assemble valve by reversing the above procedure. Note: If the main valve is worn out, (look inside cap), cleaning will not suffice, and a Replacement Cap Assembly, Hunter P/N R528 will be required.

Note: If the fill valve turns on and off by itself, or runs continuously without spilling into the overflow tube, the problem is not the valve. The fill valve is running due to a slow leak in the tank, probably caused by a flapper. Either worn out or misaligned.