Hello again,
I've got a bunch of shipping flat rate calculations that result in a single output option, all working totally fine.
Only problem is I've now introduced a 'pick up from store' which should always be set to $0, but for some reason, regardless of what I do, it always equals the same as the other option calculated.

I've created a rule that sets the shipping line item of the 'pickup' option to 0, but depending on its weight it either doesn't work, or sets both options to 0.

What am I missing?

One option's action:
Add an amount to the unit price
Parameter: Line item: [commerce_line_item], Amount: 500, Price component type: Flat Rate Towel Shipping

The other option's action:
Set the unit price to a specific amount
Parameter: Line item: [commerce_line_item], Amount: 0, Price component type: Pickup

result:
Towel Shipping: $5.00
Pickup: $5.00