I have similar problems. What ever i enter as a linetype pattern, it jumps back to 1,0 after closing and reopening the options dialog.
Maybe its a localization issue, i noticed that for example the official Dashed pattern is: 5,00, 5,00
Notice the comma as decimal place, IMO it should be 5.00, 5.00
I am using Windows 10 german and Rhino 7 English.
Also it fails to import acad.lin - it imports, but when i close the options window and reopen it, the imported linetypes are gone.
I also managed to get Rhino into a non-responsive state by playing around with the linetype pattern a few times.
Another thing i noticed, if i copy for example the Dashed linetype, the pattern is messed up, it reads: 5,00, 0,00, 0,00, 0,00, 5,00, 0,00, 0,00, 0,00
Looks like a bug to me.