I'm on 927 and 935 etc. I change revision to fit my needs. I don't have any problem myself.
But I was considering the error EnigmaXtreme encountered, and remember there was the same error on previous GX release, so I gave the workaround for that error.
I thought GX reverted back the support of cIOSx rev19 on r931, but maybe it's working with cIOSx rev20 without any update to the code ?
I didn't try 938 with cIOSx rev20 yet, but if you say it's working, that's great.
Then EnigmaXtreme, try updating USBloaderGX to r938.
Edit :
I just tried IOS250rev20 [base56], it's working too. (Tested Arc Rise Fantasia, the game play without freeze)
But I keep IOS249 rev17 as main cIOS for GX, so I don't know if there's the GX freeze bug still present.