Some weeks ago, a fellow brazilian romhacker tried running Card Mode Hack together with this brazilian portuguese translation
. He got the same problem with the spanish translation: it didn't worked.
Firstly, he applied firstly the translation patch and then the card mode hack patch. The game crashed after the "Press Start Button" screen. Then, he applied the card mode hack patch first and then the translation patch. The game didn't booted up.
Although you mentioned that none of the strings in the ROM were touched, what if the offsets of some texts and graphics of the game were moved, let's say, some bytes forward in order to gain space, then that probably should impact some translations, especially if pointers of texts or compressed graphics were somehow changed (on my translation, all texts were moved to offset 0x700000, and some compressed graphics were moved to those offsets as well).