G'day garage_remotes. We encountered the same issue with the new 250g "express satchels" (mainly with the barcodes begining with "FRE"). This was remedied - there was apparently an issue with the tracking data pushing from the carrier or the carriers scanners. This was however not the last or least of the problems. 

At the time of writing we have about 25 parcels with no movement for 3 weeks, 3 of which have formally been declared lost at the time of writing. We have stopped using them obviously (for about 10 days now). At the moment it appears sendle do not want to compensate for lost items either. 

I was a fan of Sendle until this experience - the carrier that they use for this service "Parcel Freight Logistics" does not appear to be up to the task.

It is may be a bit early to tell. I hope your experience has been better than ours.