The same issue have been reported on CZ&SK MIUI forums. That's why some people went back to Stable V4. Probably we should wait for Xiaomi to fix "Un"stable V5 to Stable V6
fo
follow this guide (it doesn't matter which stable ROM you going to use, it works on V3, V4 or V5)
http://xiaomi.eu/community/threads/english-cwm-for-xiaomi-hongmi-td-wcdma-full-working.22953/page-5#post-191083
So here you go simple step by step guide
Before you start job, put all those files on sd card:
*miuiandroid_multi_V6W_3.12.13_jb-4.2.zip
*miuiandroid_multi_HM2013023_WCDMA_JHBCNAH3.0_jb-4.2.zip
*CWM V5 NO TOUCH WCDMA Recovery (thanks to Sonik1SVK for build)
*mobileuncle.toolbox_327.apk
*root.zip...
It doesn't matter if that ROM is bug free. After you flash "CWM V5 No Touch WCDMA recovery" you will go back to stable ROM V3.0 and finally make root. Is it clear ?
I'm not sure, probably from some spanish forum... more info about that root.zip file here:
http://en.miui.com/forum.php?mod=viewthread&tid=8101&extra=&highlight=hongmi&page=5