I have had this issue thru all builds of the Beta, I am currently updated to 1.7.0.9.
I'm running MacOSX 10.14.3 but have had it on the last two OS versions as well and on a second computer (also Mac)
I have spoken to the Font Creator (a well regarded pro) and he sees no reason why this should be happening.
He has agreed to let me share his paid font with the Beta team for testing.
As you can see in the screen shots, his font have numerous alternates that work perfectly in Designer 1.6.1
However the same text (copy pasted or retyped) does not have this same choices in 1.7.0.9
If someone would like to contact me with an email address i can send the font for you to reproduce the issue.