A HP 15CE keyboard handler bug?

[Martin Hepperle]

So far I was able to lock up my HP-15CE three times.
All cases seemed to be related to pressing "some" keys (in the heat of the battle, I could not reproduce the first instances when this happened).

However, I can reproduce the last case with my unit. Is this a general problem?

Key sequence:
1.) Hold 'f' and ENTER, press ON, release f and ENTER, then ON
=> The calculator switches ON and appears normal.

2.) Now try to switch it OFF by pressing the ON key
=> nothing happens. The ON/OFF key does nothing.

3.) Repeat the sequence (with the calculator still locked in ON mode):
Hold 'f' and ENTER, press ON, release f and ENTER, release ON
=> The calculator switches off.
After this sequence, the ON key seems to work normally as it should.

Also, pressing 'f' toggles the 'f' annunciator, but pressing it again does not toggle if back to unlit. Same for 'g'. Is this intended behavior?

The sequence can occur accidentally or when one tries the self test but confuses the 'f' and 'g' keys.
Initially, before discovering the 3.) workaround, I removed batteries or pressed the reset button for recovery, but this clears the memory.

Martin