Hi Ned,, I'm using Windows 7 and have 14-18 installed on my system. Sheet metal parts export to dxf fine with both 2015 & 2018. My 2015 is SP2.1.. Not sure if this can eliminate any possibilities but it does look like a Win10 thing and not from having both 15 & 18 installed on your system.
Thanks for looking Dennis
now to delete the undelete-able windows updates
Something else that might be worth looking into is do you have a custom map file that you are using for your saving to dxf? Maybe something got corrupted? Lost? Overwritten? Maybe try Enabling/Disabling? This is a shot in the dark. I did try to fake mine by selecting a phony file (a jpeg) and it gave me a warning but was still able to export. Maybe something in the Export Options?
So the problem deteriorated even more yesterday and would not let me even export from a flat face.
Had case open with solidworks.
They closed it wtih the solution that it works in 2018 and 2015 is no longer supportedarrgghh
So i unistalled 2015 and 2018,
reinstalled a number of times trying to not cross the toolboxes over,
Tip when installing multiple versions, from installation manager rename SOLIDWORKSCorp to SOLIDWORKSCorp2015,
And Hole wizard install location from SolidworksData to SolidworksData2015
Repeat these when install later version ie 2018
This way 2018 dosent mess the 2015 toolbox and hole wizard
starting both with brand new settings, One for each version.
Now my flat-patterns are working again
Ned... isn't technology great!
(glad it all worked out!)
We have a JCB Backhoe across the yard here,
and sometimes i feel like starting it up and
crushing the Technology