Now I tried the same with the new version, 0.10.3.1, but I got the very same result. (I downloaded the binaries from the official website and I always check the hashes, they are matching. Although I cannot find the corresponding signatures in the folder where they supposed to be: source code repository /utils/gpg_keys.)

Are you sending to an integrated address ? I've just tried here and the addresses are the same. Linux/Linux though, so it could be a cross platform bug.

It can well be that it is an integrated address, thank you for the hint. But in this case, how can I be sure that the two are actually the same, and this is eg. not a cross platform bug? Is there a way to see this integrated address at the confirmation prompt when signing the transfer offline? Or alternatively can I wrap the standard address out of the integrated address on the other hot wallet machine? OK, I just found this potentially answering my own question, although I haven't tried it yet: https://monero.stackexchange.com/questions/1892/how-to-unpack-a-monero-integrated-address-using-the-command-line So if this works, and the standard addresses match, then I can just go on, sign and submit it?

I have verified here that sending a transaction to an integrated address will end up showing the real address when signing. Integrated addresses are a form of address which embed both a standard address and a short payment ID, for convenience.

To split an integrated address into a standard address plus the integrated payment ID, use:

integrated_address INTEGRATEDADDRESSGOESHERE

To compose an integrated address from a standard address and a short payment ID:

integrated_address STANDARDADDRESSHERE PAYMENTIDHERE

Then you can compare to check the integrated address and standard addresses really are the same.

Thank you, it worked out perfectly. Indeed the problem was only that the off-line wallet showed the standard address after generating an unsigned transaction with the integrated version of the same address.