Pablo before u raised the tag did u go to level low and manually raise the rear of the bus up first?
. If not your results were potentially incorrect.
Without first going all up rear and u dump the tag the back squatts so much it may alter test results.
If after u try my suggestion and the lean is in fact gone away........... that means your lean is either.
The 2 position spool valve between the drive bags and the tag bag.
OR
The tag bag
OR
The tag bag ping tank ( football)
OR
A fitting or line associated with those components.