SAVE CDR 2018 AS PDF - it saves pantone colrs but NOT Custom SPOT colors

I have Coreldraw 2018 - and sent files to printers every day as PDFs as like every printer requests.

But those jobs that require a CUSTOM SPOT COLOR - (which I have created a custom pallet with ie: spot gloss, scodix, CutContur etc) 

Anything that has the custom spot in it DOES NOT work in the PDF - when setting "save color as" to "NATIVE"

IT WORKS WITH PANTONE COLORS BUT NOT WITH CUSTOM SPOT COLORS

I have been using CorelDraw since x3 - and still isn't fixed

My get-around is to SAVE AS a illustrator file, OPEN in Illustrator and then SAVE AS pdf. - been doing for years.

I see a lot of people saying same thing but no simple fix - 

SHOULDN'T IT BE AS SIMPLE AS SELECTING A PANTONE COLOR OR YOUR OWN CUSTOM SPOT COLOR

SAVE AS PDF AS "NATIVE" AND PRESTO????????

ANYONE WITH A FIX - tried everything! - or just change to Illustrator as 90% of my work goes to offset printers.