Complex sentence: The group continued working as a five member band since 2014 when they parted ways with their first guitarist Bruno Grobelšek for no known reasons, who was replaced with Jasmin Mišić as a new lead guitar of the band.
Split into simpler sentences: The group continued working as a five member band since despite parting ways with their first guitarist Bruno Grobelšek for no known reasons. He was replaced with Jasmin Mišić as a new lead guitar of the band.