Usual things there are then a non relative encoding, 16 bit encoding (I presume you did not try that) or compression. The latter being by the far more likely.
Compression search is kind of a thing, and if it is BIOS calls you may also have SWI logs but most things there beyond the simple decompression tools are going to be graphics or maybe audio oriented. You might still use a SWI log to guide a decompression effort instead of jumping right to the assembly debugging.