Kone HR escalator

Having a issue of section of steps hitting comb plates in down direction, I'll have 5 steps hit then another section of about 3 or 4 steps hit comb plates on impact plate?
Cheked carriage tension OK checked rollers OK checked demarcation treads on steps ok. What am I missing.
Like I said it only hits 5 steps and then a couple steps go by then another 3 or 4 steps hit. All other steps are fine coming in to comb impact.

Two sections of bad chain.

That's what i was thinking, thanks
Can I replace just sections or the whole step chain?

I would renew both step chains

Recommended: all chain. But I'm not the Boss. If you do partial problems could be worse. I've done a lot of chain.

Thanks, we are replacing both