I assume it's P/S elements you use. I use an old version, PS CS4E, which in Edit-Preference=Performance, gives you the opportunity to fine tune. You may have something similar perhaps? It appears this may be linked to Windows, they may update to cure. I do get this on Windows XP Pro, but it is genuine, as XP only sees about 3.5 Gb memory, no matter how much you have. Computer has a dual boot, and on Win 10, 1803, sees the 8Gb I have. Clearing the Cache, is worth trying, again if possible.
There appears to be a work around, Found this, but it involves registry editing, if in doubt, don't. Make a System Restore point before any attempt is made, by anybody!
Here is a Link to where I found this info.
If you are into P/S , then sometime worth expanding your memory, again if possible, surprised if not. memory is fairly cheap nowadays.
Running the Crucial Scanner, link below, will give you memory info.