Just wondered. Did you bring in a configuration, or did you set the Seke's up in v18, also what workspace are you using, (tools - customise - options - load from). obviously v18 doesn't have LTE mode, but it does have different config's.
I only ask, as I did a test, setting the Seke 'p' to parallel line, and it worked ok. it did warn that 'p' was already set to polar coordinates but I chose to reset it. One other thing I noticed though, in your screen shot, it shows the Keep Length' icon, + you also have a 'multiple' icon, which I do not have in v18 (nor 2018 for that matter).
When installing v18, did you also install the two patches from the forum updates page. If yes. I'd try loading a configuration, and if that didn't work, I'd try deleting the built in folder, then seeing what happens.