Whilst the SH2 may not be the best for everyone, it can accommodate the Fibre 900 package. However, BT needs to tweak the settings to make sure you're getting the best our of your package.
Whilst not an expert, my suggestion is to try a staged approach.
I would firstly check your ip profile. For this you will need your BBEU which BT should be able to give to you. Run the BT Wholesale speedtest (ignore the speeds reported). Select 'Additional Diagnostic' and select 'BBEU' before entering it. this will give you a report like this:
As you can see, this will give you the maximum speeds you can achieve. If your max download is lower than above i.e more reflective of what you are achieving, your package has not been set up correctly.
If the above test looks right, I would check your speeds as others have suggested by connecting your laptop directly to the ONT, bypassing the router. How to do this can be found in other posts. If this shows your speeds being nearer to the advertised speeds you'll know that the problem is more likely to be the router. It may not be faulty, just that BT hasn't made the right parameter adjustments. These will show in your Hub Manager event log when you filter by TR069. The Hub checks in with BT daily, every 24 hours after any reboot.
Hope that helps and good luck.
