Toto Drake Flush/Fill Pause

Hello , we had 4 Toto Drakes installed in our new house about 2 years ago.
Lately one of them has been behaving differently then the others during
a flush.

When we flush it , it empties OK but then it "delays" with 2 to 3 seconds of silence before it starts to refill. I guess the best way to say it is that it pauses... All the other Toto Drakes start to refill almost immediately after
the tank has emptied. I lifted the cover to look inside as it flushes and did not
notice anything.

Is this a sign of some impending failure of the flush system? If so any ideas
on what needs replacing? I'm guessing its the blue flushing "module". We have no plumbing experience

Thanks!

The fill valve may need cleaning,

or you can replace the assembly cap, which sells for $1.99 at Lowes.

Instructions are here.

I had one that did that...it stopped on its own. It's been a couple of years now. I wouldn't worry.