Error while syncing with the blockchain on my Raspberry Pi
As @MartinSolie noted, it might be helpful to look into the debug.log file.

Based on what you describe, it sounds like your Bitcoin Core node crashes at some point while synchronizing. You mentioned that you copied the chain from another device. Since you mentioned you are waiting for the blocks to match the headers, I'm not sure the transferred chain is correctly recognized by Bitcoin Core. Your Bitcoin Core is either re-indexing the whole chain or even downloading it. On a Raspberry 3 this can take quite a while (i.e. multiple weeks).

Bitcoin Core probably crashes, because it runs out of memory. One way of solving that would be to add a SWAP file on your HDD (don't do it on the SD Card! Swapping kills the SD card over time).