Ambrose said:

All eight castles across the two main servers. 50 per cent bonus initially lowers time, but 3 hrs later the time has reverted back to the original time minus 3 hrs...e.g. 8 days 22 hrs..boost becomes 5 days 22 hrs.roll on three hours and time is back at 8 days 17 hrs..6 hrs difference. Boost again to 5 days 19 hrs.

This is a Current ongoing issue.

Regards

Stephen

Hello Lord Ambrose , is not a bug ! all the bonus  in the Dragon Stone are active for 3 hours, after that you have to log in the game again and activate again your dragon !

I wish you good game and good battles !