I have also been plagued by this problem since the 1709 update. It is indeed the SilentCleanup task which is deleting the thumbnail cache. This task should only run "when free disk space is running low", it has no triggers of it's own and so is being trigger in error by another process (even though there is ample free disk space).
Rather than disable the SIlentCleanup task completely, you can stop it being triggered by Explorer. To do this, run Regedit and browse to the following path:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Thumbnail Cache
Modify Autoruns DWORD and set its value to 0 and reboot your computer.
I can't find Autoruns DWORD but I do see Autorun REG_DWORD in VolumeCaches\Thumbnail Cache
Is that the same
Please reply
Steve