Reinstalling M4, M4 Morphs++, and M4 Elite Ethnic Faces from scratch seems a sensible idea. But Dave Allen's (the Irish comedian) advice springs to mind here - "If I were you I wouldn't start from here!"... In this case 'Here' is with M4, M4 Morphs++, and M4 Elite Ethnic Faces already installed in one of your runtimes, but not working correctly.

An approach that might completely side-step the corrupt files problem is to delete them, but NOT manually - instead use the appropriate DAZ UNinstallers. Then you can do a clean reinstall of M4.

N.B.  I've never used the DAZ UNinstallers myself, so what follows really needs confirmation from somebody who has...

Provided certain conditions are met you may simply be able to uninstall the problematic products which should get you back to a clean starting part. The conditions (I think) are:
If (a) you originally used the DAZ installers, and (b) during installation you selected the option to include an uninstaller (I think the 'default' option does that too), and (c) you didn't manually move any files after installation, then you should be able to get rid of the not-working M4, M4 Morphs++, and M4 Elite Ethnic Faces files by simply running those uninstallers. But as already stated I've never tried that myself - can somebody else confirm whether that's a sensible suggestion?

However, if you manually moved or renamed any of the files after installation then the uninstallers may not work at all, or they may do part of the job but require you to manually remove what's left - once again can somebody else give advice on that?

Regarding the file corruption - if it's restricted to the M4 Morphs++ related files I'd keep my fingers crossed, consider it as simply bad luck, and try to side-step the problem as noted above. But if you start seeing corruption in other Poser files, and/or non-Poser files, and/or inexplicable problems with other software then it might be something else.

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.

*also available in ShareCG, DAZ, and HiveWire3D flavours (the DeviantArt and CGBytes flavour have been discontinued).