I went through the Weapon Unleash plugin and it does have 2 lines pertaining to selectNextCommand. They appear when replacing the skill ID used for Attack and Guard in Scene Battle. Hope this clears things up?
Viewing post in Bug - RMMV DTB linked function broken
Wow, I actually found Weapon Unleash in a download from ages ago, and the issue is not even close to anything I expected. In essence, it's a... bug? maybe? in Weapon Unleash that may or may not affect things normally (still piecing this mess together), and to be honest, I'm a little surprised it works when Dualtechs ISN'T installed.
I'm still piecing things together, but the Dualtech is being resolved when it isn't supposed to be. Actually, I'm not even sure it's necessarily Weapon Unleash that has it wrong, but something isn't communicating correctly with other things.
EDIT: I'm understanding a little better what's going on here, and... I'm not actually sure it's a bug in Weapon Unleash OR Dualtechs individually, but it's certainly a weird interaction when both are together.