Operatingsystem and Medium host parameters change after build

i cloned OS and HOSTGROUP for new variation,
after Host installation OS revert to original OS(or default name?) so using BUILD again will not work.

Expected outcome:
host parameters will stay as configured by hostgroup

Foreman and Proxy versions:
Version 3.6.1

Other relevant data:

steps to reproduce:
* also here i noticed changing only minor version and description allow same name for OS
(steps 1-3 with the .9 are to demonstrate the steps i originally did with .3)
1)clone OS:

2)change only minor version and description:


3)clone the Host group and install Host with it.

4)after installation+ansible done i can see this audit message:

and details OS card change from:


and trying to rebuild i get this:

all templates parsing failed with “Failure parsing : undefined method `medium_uri’ for nil:NilClass.”

what is the mechanism causing this change and how can i control or prevent it?