I’m not really the best person to answer that, but I’d put a guess on that the store may be throttling downloads temporarily to prevent resource exhaustion, but there could be other explanations such as you might be following a short lived branch such as hypothetically latest/stable/ubuntu-22.04
Whether this one specifically exists, I’m unsure; but some snaps baked into the Ubuntu releases tend to have the pattern of using a branch release specific to the distributions release, which later realigns with latest/stable
but at any given point might actually be slightly different to it.
Try
sudo snap refresh --channel latest/stable snapd
In the general case however, I’d expect it would update itself as expected eventually