Steps to replicate issue (on my real system):

1.

• template 'home HW' linked to template 'Template H'
• hosts linked to template 'Template H'

2.

• adding item 'ethernet media speed $1' to the template 'home HW'
• there is item 'ethernet media speed $1' in template 'Template H', description 'home HW:ethernet media speed eth0'

everything is just fine

3.

• moving item from template 'home HW' to new one 'home network eth0 HW' which is not linked to template 'Template H':
  a) edit item
  b) select "Host"
  c) select template 'home network eth0 HW'
  d) save

4.
in result:

• there is item 'ethernet media speed eth0' in template 'home network eth0 HW' which is NOT linked to template 'Template H'
• there is item 'ethernet media speed eth0' in template 'Template H' (item description: 'home network eth0 HW:ethernet media speed eth0') which is wrong