First, your C drive is about to reach the critical level. Be cautious, clean up some data from it. Move the user files elsewhere.
Next, you have MSE installed, which is not for Windows 10. Uninstall it as you have Windows Defender.
Also, please check in Lenovo supported systems list for Windows 10 Upgrade - Lenovo Support (US) that your 9953CTO ThinkCenter xxx is officially supported for Windows 10 or not. If not, some problems like this may arise. In that case I would suggest you to have a communication with Lenovo.
MSC "c:\program files\microsoft security client\msseces.exe" -hide -runkey Public HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
And, as it is bugcheck 50 with no adequate flagged driver (FLTMGR.SYS is a system driver and not a cause of a BSOD), test your RAM modules for possible errors. Run memtest86+ for at least 8 consecutive passes.
If it start showing errors/red lines, stop testing. A single error is enough to determine that something is going bad there.
Take a camera snap of the memtest86+ window before closing the program. Let us see it.
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