VTR - Panther & Arrow XL

We've just noticed a drop in our VTR since 18th February as valid Panther tracking numbers are now flagging as invalid. Panther (AIT) are advising of no change within their system so it looks to maybe something within Amazon that's changed. Is this something others are experiencing?

Invalid tracking flags are an issue we've had with Arrow XL historically despite Arrow XL also supposedly being an integrated carrier. At the time we switched freight to Panther but this is not sustainable to move 2-man services as Amazon makes them unusable.