Volvo I-shift problem

Hello, We have a 2005 Volvo fh12 with i-shift gearbox with very slow changes, otherwise its lovely up and down with no issues, and smooth with no bad noise ect and no fault codes...

but it changes way too slowly and when plug in volvo software and try and run a gear shifting test, it times out saying "taking too long to shift",

(for example if i was driving a manual and put the clutch down like normal and then took a few seconds before i selected the gear and let the clutch out, that's what it does....

its a major issue as fully loaded it will get stuck in an endless cycle selecting a gear and then back down to a lower gear where its lost the momentum!

any pointers would be greatly appreciated