The VOIDRUNNER'S CODEX is coming! Explore new worlds, fight oppressive empires, fend off fearsome aliens, and wield deadly psionics with this comprehensive boxed set expansion for 5E and A5E!
AFAIK:
Shield Expert (from Sword and Fist) does not allow you to retain your buckler bonus while fighting with two weapons if you attack with the off-hand weapon.
Nope it sure doesn't. It allows you to maintain the shield bonus if you use the shield as a weapon (AKA shield bashing), which you cannot do with a buckler.