Linnworks is not sending tracking URL's to Shopify.
Where no tracking URL is sent, Shopify tries to match to a courier as best as it can - however this is not always correct.
For us, this impacts hundreds of customers each week, as both their shipping confirmation emails and order status pages take them to an invalid tracking URL.
In turn this creates customer support issues as team members spend the day explaining the problem to customers and passing them the correct URL to use manually.
Linnworks support have confirmed that there is already a development card for this, but the developers have not yet picked it up. It all depends on the amount of requests as well as other cards with a critical priority.