[Autumn]

It seems as though an update has made it so that Sub-weapons being fired from an Arbalest's cannon skill are still being counted as being "Equipped", even though the slot in your equipment is completely empty.

This makes it so that Rifles/Howling Handshot cannot gain 2hand bonuses when firing their off-hand weapon, but beneficially this also means that Lare Grystale still counts as a shield and Vent Petale still applies.

This also makes it so that Arbalest loses a potential class synergy in Monk (this is copium though)

A quick and easy test of this was done with Lare Grystale and Enchant Shield still being accessible (and 2hand not applying) as well as:
-Not losing Vent Petale bonus stats
-Equipping an Ensui and keeping the visual effect and damage reduction

[Neus]

This should be corrected in 2.87 v3.