In the process of artificial selection of breed groups, inbreeding is used as a tool. Basically, if you are not experienced in breeding work, you should better avoid it. However, a single entry into the retraction does not have any critical consequences.
The imbreeding threshold for canines is generally quite high. It is not uncommon for wolf families to practice inbreeding in the wild. The high threshold of inbreeding for these species is part of the natural adaptation mechanism.