Originally posted by MarioFanGamer
It's mostly because at some point (more specifically, Asar v1.80), Asar throws a warning when ROM mappings are switched within a single patch. The main cause is SA-1 compatibility: Most patches are hybrid patches i.e. they both support LoROM (ROM without SA-1) and SA-1 (ROM with SA-1). Some patches do this by first declaring themselves as a LoROM and then check whether they detect SA-1. If so, change the mapping to SA-1.
This doesn't appear on every patch because some check for SA-1 immedietly and then decide which mappter to chose.
Either way, it's a warning which you can dismiss since it already was fine before. It is an issue if some data is already written but such a patch is badly written and wouldn't be accepted anyway unless it flew under the radar for some reason.
Thanks for clearing that up m8!
currently working on The Amazingly Randy