While Hyperion Entertainment specifically documents that one no longer needs to specify MaxTransfer speed (see: https://www.hyperion-entertain…eed-to-manually-adjust-it)
I can confirm, after playing around for the past 2 days that it is very much still required when using CF cards, especially with my ACA1230. I was getting strange behaviour (mostly WHDLoad telling me it's out of memory for some games, unsupported instruction, or even corrupt image!) When I set the MaxTransfer speed to 0x1fe00 and used the filesystem that ships with 3.1.4, all problems went away. Even the 18.104.22.168 update did not fix this issue.
Just set MaxTransfer speed and be done with it.
Sharing it in case anyone else runs into this issue in the future.