Double Encryption Q

[COMINT]

Quick system scenario:

You have packet [A].

It gets encrypted using an AES algo in a particular mode and we are
left with [zA].

More data [B] is added to that encrypted packet.

Now I have [zA]+[B] in one packet and I re-encrypt it with the same
algo/key/mode.

Have I just compromised the security somehow? I wasn't aware of
anything but something about this double encryption made something
ring in my mind so I wanted to double check...

Many thanks,

Mr Pink

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