AM3703: replacing Lpddr memory issues

Part Number:AM3703

Hello everybody , 

please  my board is based on AM3703  in CUS package . 

Now I need to change memory  going from  micron  to ISSI 

so  from Micron  MT46H16M32LFB5-6 IT

to  ISSI         IS43LR32160C-6BLI 

i m using a 133MHz clock and only first 32MB . 

now  boards fully working on Micron chips now I have issues on the ISSI  based   ( many of them ) .

please  any raccomandation / suggestion ?   I already checked  our  section “6.4.2 SDRAM   and everything  seems to be ok ...

as further indication  using higher driver strenght on am37xx  seems to  partly solve the issue .

any idea/suggestion is very welcome 

thank you 

regards

Carlo