Please follow the below steps.
> Launch Lightroom
> Click on Edit > Preferences
> Click on File Handling Tab
> Click on Purge Cache for Video Cache Settings
> Restart Lightroom and check for the issue
Let me know if this helps.
Sorry but this has not changed the cache size.
My version of Lightroom is 6, and I have selected the option to limit the size of the video cache to 3Gb.
Does anyone know how to get support from adobe?
If LR doesn't allow you to set where the folder is, then you could try using a junction point if you're using the NTFS file system on your drives. The MKLINK command should work on Windows versions newer than WinXP (Vista or later).
It's actually pretty straight forward. Here's a decent description: