shift bump button deleting sub master on Element

Hi all,

had a strange one: pushing bump buttons and shift  on my element an deletes the corresponding submaster. Don't know if this is wanted or a bug!? I have been/am using shift&clear a lot during busking on the ION whilst bumping buttons (during busking) never had a problem with it. happened now on the element running 2.9.1 build 17 but not on the ION running v3. it is not showing up in undo. just deletes the sub.

attached log file should show  sub 7+8 at 14:29 on 09/30/2020 being deleted.