Btw, it's 1 am at my time so I may response few hours later ;)

No worries. I tried dual wielding with the mod list you specified, same order and everything. Still didn't work, here's the log:
https://gist.github.com/HugsLibRecordKeeper/7241ba1fd98c3fd5ede98a707dec726c

Also, I've been using Run and Gun on my personal mod list, so the majority of the testing I've done has been with that included.

Originally posted by Vanidas:

No worries. I tried dual wielding with the mod list you specified, same order and everything. Still didn't work, here's the log:
https://gist.github.com/HugsLibRecordKeeper/7241ba1fd98c3fd5ede98a707dec726c

Also, I've been using Run and Gun on my personal mod list, so the majority of the testing I've done has been with that included.

That's really odd... how come under exactly same condition the result is different...

Let me isolate the issue;

1. Did you add weapon directly to the pawn (like by pawn editor) or let the pawn equip them from the ground?
2. Did your pawn not have any backstory that disable their melee combat?
3. Did you removed older version of Dual Wield and fresh installed (subscribed) new Dual Wield after unsub / delete older version?

In my environment, the log looks like below screenshot and it works without issue.

https://imgur.com/hM41WPt

Originally posted by emitbreaker:

1. Did you add weapon directly to the pawn (like by pawn editor) or let the pawn equip them from the ground?

I've tried both, both had the same results.

Originally posted by emitbreaker:

2. Did your pawn not have any backstory that disable their melee combat?

Definitely not, that's always the first thing I check.

Originally posted by emitbreaker:

3. Did you removed older version of Dual Wield and fresh installed (subscribed) new Dual Wield after unsub / delete older version?

By older version, do you mean the other Dual Wield mod on the workshop that's not labeled [dev], or an older update of the [dev] version? Because I unsubbed to the older version a while ago. I'll go ahead and try unsubbing and resubbing to the [dev] version and see if that makes a difference.

Edit: Tried unsubbing and re-subbing, didn't make a difference.

Hmm... which combination of weapons did you use? I tested with Prosperine Khopesh, vanilla knife with Necrodermis / Plasteel, Power Sword (CU) and bolt pistol (CU) but all works fine at my end, or at least I can click the Gizmo and attack target with no issue.

Originally posted by emitbreaker:

Hmm... which combination of weapons did you use? I tested with Prosperine Khopesh, vanilla knife with Necrodermis / Plasteel, Power Sword (CU) and bolt pistol (CU) but all works fine at my end, or at least I can click the Gizmo and attack target with no issue.

I always test with the Bolt Pistol (CM) in my main hand and the Power Sword (CM) in my off-hand. I tried testing with the Khopesh a few times, result is pretty much the same. Also, the Necrodermis knife is really inconsistent for me. The first couple times I tested it, I couldn't dual-wield with it, but when I tried to duplicate my results for the log, it worked fine.

One more question - did you click the gizmo and select target at your end? Or spawn enemy and wait until pawn automatically attack them?

Originally posted by emitbreaker:

One more question - did you click the gizmo and select target at your end? Or spawn enemy and wait until pawn automatically attack them?

Oh ♥♥♥♥, I finally reproduced the issue. It seems like this case only happens if you put Bolt Pistol as primary and power sword as off-hand - to be honest, I put them in an opposite way.

I think something with my pistol causes this issue. Let me look into them.

Looks like the issue happens when pistol or ranged weapon is placed on primary and power sword or other two-handed yet can be configured as off-hand melee weapon is placed on off-hand side. I think this may takes time to solve, but for a work around, would you put melee weapon on your primary and ranged as off-hand?

It's quite confusing because the same melee weapons from other mod won't trigger the issue...

Originally posted by emitbreaker:

One more question - did you click the gizmo and select target at your end? Or spawn enemy and wait until pawn automatically attack them?

Usually, I just draft them and check and see if the melee attack button is grayed out. Earlier in my playthrough, I tried positioning a pawn with a dual melee and ranged weapons next to an enemy and waiting for them to auto-attack, which didn't work. I also tried right-clicking and selecting melee attack from that menu, but the button didn't show up.

Originally posted by emitbreaker:

Oh ♥♥♥♥, I finally reproduced the issue. It seems like this case only happens if you put Bolt Pistol as primary and power sword as off-hand - to be honest, I put them in an opposite way.

I think something with my pistol causes this issue. Let me look into them.

It's possible this changed with the new version of the mod you put out, but I tested it using vanilla ranged weapons and melee weapons from your mod and got the same result. I'll go ahead and test it again using a vanilla ranged and modded melee, plus a modded ranged and vanilla melee, see what happens.

Originally posted by emitbreaker:

I think this may takes time to solve, but for a work around, would you put melee weapon on your primary and ranged as off-hand?

I've tried that before. If I do, the melee weapon works fine, but then the ranged weapon stops working.

Just gave it a whirl. Vanilla ranged + modded melee doesn't work. Modded ranged + vanilla melee works fine. I tested it with the Bolt Pistol (CM), Power Sword (CM), vanilla Autopistol, and vanilla Uranium knife. I also tested it with a Necrodermis knife and it worked fine.

Originally posted by Vanidas:

Just gave it a whirl. Vanilla ranged + modded melee doesn't work. Modded ranged + vanilla melee works fine. I tested it with the Bolt Pistol (CM), Power Sword (CM), vanilla Autopistol, and vanilla Uranium knife. I also tested it with a Necrodermis knife and it worked fine.

I narrowed down the issue - seems like Dual Wield's harmony patch makes some trouble when a melee weapon has attack with armor penetration. All vanilla melee weapons doesn't have any, so now I'm trying to check with GrimWorld's weapon.

My current theory is either Armor penetration on melee weapon or 0 valued armor penetration on melee weapon causes the issue.

Either way, partially because of not so good coding. Let me check how to avoid this issue.

Bingo. Any melee weapon that has attack with Armor Penetration on Off-Hand side causes the issue. I just confirmed with GrimWorld's Astartes Power Sword which also has the value on it.

Sadly, it's the mod's issue and I can't solve it unless I entirely re-design my weapons.

I just checked the mod's page but it seems like the mod is long abandoned with [Dev] on title. I suggest not to use that mod.