Getting wrong base 64 encoded payload


I have a Digital matter sensor node device and the base 64 encoded data received from this end devices seems to be wrong for me…I Am supposed to receive AA== and AQ==

But I am receiving some invalid data (for ex, Rw== 8g==) …This is happening with this device alone and all the other devices seems to be working fine…Is this a problem with device or is there any other setting in the network or the application server that need to be changed…

Can someone help me out with this?