I'm getting the following error while using a swing timer (https://wago.io/-WCbLx83B) and a battle shout reminder WA:

Message: Interface\AddOns\WeakAuras\GenericTrigger.lua:1606: attempt to perform arithmetic on local 'offSpeedNew' (a nil value)
Time: Fri Oct 25 21:17:25 2019
Count: 12
Stack: Interface\AddOns\WeakAuras\GenericTrigger.lua:1606: attempt to perform arithmetic on local 'offSpeedNew' (a nil value)
[C]: ?
Interface\AddOns\WeakAuras\GenericTrigger.lua:1606: in function <Interface\AddOns\WeakAuras\GenericTrigger.lua:1588>
Interface\AddOns\WeakAuras\GenericTrigger.lua:1668: in function <Interface\AddOns\WeakAuras\GenericTrigger.lua:1664>

Locals:

I've unloaded the swing timer wa, yet I still get this error.

Can you try the alpha version of weakauras ?

Sure, how can I download it?

Well so far I have no issues with the alpha version :)

If you use twitch app you can right click on the addon and change "Release Type" to alpha channel.
Or you can direct download it from https://www.curseforge.com/wow/addons/weakauras-2/files or https://www.wowace.com/projects/weakauras-2/files

I've downloaded it, but I have an idea what may cause the issue. I get the error when I'm getting aggro and changing from berserker stance to defensive stance and I change my off-hand weapon to my main hand and equip a shield into my off-hand.
I'll test it with the alpha version now.