Very harsh air suspension

Hi guys ,

im new to forums and wonder if could get help to solve suspension problem to my a8 4.2fsi 2010 ( D3 )

Ive noticed that suspension became hard and very unpleasant after rear height sensor change and battery being disconnected .My mechanic said its shock absorbers need changing . Car feels very hard and when switch to dynamic mode can loose my teeth ! 

I have VCDS and have no error codes or leaks in suspension .Tyres are no problem as it is same set when problem started .I have done calibration few times in the last 6 month but no change in having smooth suspension back . Also recently have when in dynamic mode all options greys out in settings ( lift / comfort / auto ) and comes back Ok when stop or slow down to few Mph . 

I read somewhere that after disconnecting battery shocks can go to emergency mode / hardest option to keep car up ? Anyone heard that ? After suspension need to reset / relearn `Damper velocity ` or something . Could it be suspension control module ? 

Thank you 

Aldas