Hi. My guess is that snapcraft starts other processes that stick around after it closes. Snapd checks if a snap is running by looking for its cgroup scope, so if there a snap leaves processes hanging after it exits, the snap is thought to be running. If you could, when this happens again, please run systemctl status and look for a snap scope named something like “snap.snapcraft.*.scope”. If you find anything, please copy the entries under that scope and paste them here. That would help us confirm this hypothesis.
Thanks