Clear massive system data file on LG G3

I have somehow run out of space on my LG G3. Under storage under Misc I see have a 6.34GB System Data file. I tried dialing *#9900# as suggested in Low on Space, "System data" huge! in order to delete the dumpstate/logcat but when I dial *#9900# it tells me it's an invalid MMI code. Note that my phone is not rooted. I can get to the hidden diagnostic menu using the international code shown on [Gadget Hacks](https://lg-g3.gadgethacks.com/how-to/unlock-hidden-menu-run-diagnostic-test-your-lg-g3-0156740/) , i.e. 3845#*855#, however I can't see any menu items that look like they might clear that system file. Any ideas?