The EZTeam released a new version of their EZ4 loader, it seems to be aimed mostly at those with the new GBA sized microSD version but it should work with any EZ4 model you might have.
The changelog is as follows
The 254 issue is seemingly more for those with the new EZ4 microSD model but those with the same issue with 2013 versions might also wish to try it. *update* GBAtemp user migles confirms it fixes the 254 hang on a 2013 miniSD model.EZ4 1.76 changelog said:fixed the halt at 254Mbit when writing a 256Mbit game
improved the compatibility
improved the saver
It is unknown what "improved the compatibility" entails at this point, mostly likely a slightly improved soft reset capability (you can do a hard reset by holding L and A to launch the game, this tends to allow games like Yoshi's Island to launch properly).
EZFlash.cn download section
Filetrip download
Discussion thread
Thanks to mbmax for the news.