Is it normal to smell sewer gas from a plumbing vent?

We have a second floor room that is centered on top of the house – but this means that the windows of this second story are ABOVE the plumbing vents from the first floor. These plumbing vents are a few feet below the windows and perhaps ten feet away, laterally.

On a regular basis, a sewer gas smell comes into the second floor, presumably from these plumbing vents.

This seems like an easy problem to solve – I see some activated charcoal vent caps that are advertised to solve this very problem. Should be simple.

However, before I just cover over this problem, should I be worried that we’re regularly smelling sewer gas from these vents ? Is that indicative of some deeper plumbing problem ? Or is it totally normal for some plumbing installs to just burp sewer gas out the vents during normal, day to day operation ?

Thanks.