Is it still the same band/group?

Not really sure if I can ask this here, but I'm actually curious about it

If a band/group constantly switches their musicians, such as guitarist, bass player, drummer, etc, but not the lead singer, similar to Twenty One Pilots, is it still the same band/group? -or- If the band/group loses their lead singer, but still has the same musicians, somewhat similar to Linkin Park, is it the same band/group?

Similar to the theory on the ship of Theseus