There might be a couple things to check. Mp12 was flawed, and pulled from downloads, so you should try the latest version (10.4.0). That would be the first thing to do. After that, we may want to try disabling Secure Boot, and make sure the system has Hibernation and Fast Startup disabled.
Make sure Dell Data Protection is uninstalled, as it contains an encryption feature which could cause a conflict as well.
Lastly, check the drive model. It may be a model which has hardware encryption capability, in which case this might be causing a conflict. Please post the drive model here, and I can also take a look in our bug reports. My gut feeling right now is that it is a Samsung PM 951, as that is what is issued with most Dells lately. The OEM version may have a firmware problem (has not yet been determined at this time). A replacement/aftermarket drive may work perfectly fine. This is the only specific drive I have been seeing a lot of problems with lately.