Lightroom Classic Disk Space Error

[Matthew24266150shmf]

I am having Lightroom Classic after working for a short time pop up and say there is not sufficient space. It says it needs 20MB on the C drive. When I check my C drive it has 18GB free. The pop-up will not go away and I need to force close the program. I checked a similar post and it said to clear the trash bin, which did not help. It is popping up when i am doing all sorts of things. One time on a panorama merge, once while using a masking brush. It is using the most up-to-date version. Any help is appreciated. 

[GoldingD]

I assume your catalog is on drive C. How large is that drive? LrC needs at least 20%, some say 25% free space. I doubt that 18GB represents 20-25% free space.

Where do you keep your photos? How much free space is available on that drive?

Some notes on drive selection.

The catalog is best kept on you fastest drive with sufficient space.

The Camera RAW CACHE is best kept on your fastest drive, For Windows OS try to avoid the drive with the Windows Paging file, typically drive C, as they will compete on read/wrights

The photos can be anywhere, Drive speed not a factor.

[Matthew24266150shmf]

Yes, it is the C drive. It is under 20% free. I keep all photos on the D
until it gets full then I move them over to an external drive. The D has a
lot more space and is about 50% free currently. Can I change it to
reference the D instead of the C?

[GoldingD]

see:

https://helpx.adobe.com/lightroom-classic/help/create-catalogs.html

and just in case:

https://www.computer-darkroom.com/lr2_find_folder/find-folder.htm