Need insights in sleep routines and schedules

Hi friends,

I have a friend who has an 8 month old and we see each other almost daily. I think every 2 or 3 weeks it seems like her baby really has bad nights (as in waking up every 2 hours). She tells me that it's because there are so many nights where the baby didn't have one afternoon nap or something in bedtime routine was not followed e.g didn't have a bath or he wasn't changed into his pjs.

I'm curious, at this age is this normal still for babies to have such irregular sleep patterns still even if there is one change in the bedtime routine that would completely affect the baby's sleep. I get the nap bit cos of overtiredness but dysregulation I routine? Are there other mums with the same issue?

Thanks.