NHS Pension Input statements - errors and inconsistencies

One of my NHS practitioner clients has been provided with widely different figures for the same tax years for pension inputs in two consecutive pension input statements.  He has queried with NHS pensions and they can provide no sensible explanation and we do not know which figures are correct, which means we cannot work out if there is additional tax to pay or not.  I wondered if this was a widespread problem.  These are the figures he has been given for pension inputs:

Tax year 2013/14 :  Tax year Statement provided October 2016: £43,739.20 but sttatement provided December 2017: £87,034.87

Tax year 2014/15:  Statement provided October 2016: £63,688.28 but statement provided December 2017: £25,341.93

Tax year 2015/16 (not so much of a difference): Statement provided October 2016: £34,810.20 but statement provided December 2017: £34,943.38

 It's clearly not satisfactory that the information is not consistent and no explanation is forthcoming.  I have never had much faith in the figures provided and this makes me doubt them even more.