calc headers unable to type h,r,o,f,c as text in header or footer

When typing in the text area of headers or footers the characters h,r,o,f & c (lower or upper case) can not be entered as they immediately perform the Help,Reset.OK,Footer & Cancel functions. The header & footer format is ‘Customised’. Version (x64); Windows 10 (up to date). All other characters appear as text as normal. Example: I can not type the word ‘general’ because when I get to the ‘r’ it resets & the ‘gene’ disappears.

This seems to be bug #tdf127219