Defender Engine wont install when TMP set to RAMDISK

We have a problem Windows Defender Engine update on Wyse 5070 TC with W10 2016 LTSB, build 14393.3204).

During manual install, Windows Defender engine unpacks on TEMP path. It turned out that if we manually set TEMP and TMP variable to C: disk or USB stick, Defender Engine installs without problem with UWF OFF or ON (correct Exclusions are set).

It seems that problem is with WyseRAMDisk. I changed size and letter but it makes no difference. Any help would be appreciated.